Develop Reference

Child flex Container doesn't want to respecting its parent container

I want to achieve a proper card with proper padding around the side but it doesn't work out. the problem is the flex content container won't respecting the parent (card) by resizing the margin or reducing the distance or else. It won't resizing or following the properties. I try separately reducing the text size but doesnt work either.
$(".owl-testimonials").owlCarousel({
loop: true,
item: 3,
startPosition: 1,
center: true,
autoplay: false,
autoplayTimeout: 3000,
autoplayHoverPause: true,
});
.owl-testimonials {
margin-bottom: 30px;
}
.testimonial-card {
height: 100%;
text-overflow: ellipsis;
overflow: hidden;
padding-bottom: 20px;
width: 100%;
padding: 20px;
display: flex;
flex-direction: row;
border-radius: 20px;
background: white;
box-shadow: 5px 5px 15px rgba(0, 0, 0, 0.9);
text-align: center;
align-content: space-evenly;
justify-content: center;
transform: scale(0.5);
transition: transform 0.3s cubic-bezier(0.4, 0, 1, 1);
}
.owl-item.center .testimonial-card {
transform: scale(0.8);
background-color: rgba(255, 255, 255, 0.9);
box-shadow: 10px 10px 15px rgba(0, 0, 0, 0.9);
}
.testimonial-content {
height: 100%;
display: flex;
flex-direction: column;
}
.testi-img {
width: 100%;
height: 100%;
position: relative;
}
.testi-title {
color: wheat;
filter: drop-shadow(0 0 0.75rem #000);
text-align: center;
border-radius: 40px;
margin-top: 30px;
padding: 30px;
width: 30%;
margin-inline: auto;
font-weight: bold;
font-size: xx-large;
}
<h3 class="testi-title"> Testimonial</h3>
<section class="owl-carousel owl-testimonials">
<div class="testimonial-card">
<img class="testi-img" src="images/team/team2.jpg" alt="Testimonial 1">
<div class="testimonial-content">
<h4>Bu Irma</h4>
<h5 class="date">Dosen</h5>
<p>
Lorem ipsum dolor sit amet consectetur, Ducimus, repudiandae temporibus omnis illum maxime quod deserunt eligendi dolor
</p>
</div>
</div>
<div class="testimonial-card">
<img class="testi-img" src="images/team/team1.jpg" alt="Testimonial 2">
<div class="testimonial-content">
<h4>Pak Andre</h4>
<h5 class="date">Kontraktor</h5>
<p>
Lorem ipsum dolor sit amet consectetur, Ducimus, repudiandae temporibus omnis illum maxime quod deserunt eligendi dolor
</p>
</div>
</div>
<div class="testimonial-card">
<img class="testi-img" src="images/team/team3.jpg" alt="Testimonial 3">
<div class="testimonial-content">
<h4>Pak Budi</h4>
<h5 class="date">Pedagang Bakso</h5>
<p>
Lorem ipsum dolor sit amet consectetur, Ducimus, repudiandae temporibus omnis illum maxime quod deserunt eligendi dolor
</p>
</div>
</div>
</section>

The text-overflow won't kick in until your text overflows first.
Change this:
.owl-item .testimonial-card {
height: 300px;
text-overflow: ellipsis;
}
To this:
.owl-item .testimonial-card {
height: 300px;
overflow: hidden;
text-overflow: ellipsis;
}

Why is my card overlapping the fixed nav when I hover it?

I have a problem when I hover my article with class="card" name inside my div class="container", it looks like the article overlaps the nav. How do I fix this without removing my transform scale in .card:hover? I want to make it without overlapping with the nav when I hover over it.
window.onscroll = function() {
myFunction()
};
var navbar = document.querySelector(".myNav");
var sticky = navbar.offsetTop;
function myFunction() {
if (window.pageYOffset >= sticky) {
navbar.classList.add("sticky")
} else {
navbar.classList.remove("sticky");
}
}
#import url('https://fonts.googleapis.com/css2?family=Quicksand:wght#400;500;700&display=swap');
* {
text-decoration: none;
box-sizing: border-box;
font-family: sans-serif;
}
body {
background-image: url('/Website/Images/SPY_X_FAMILY.jpg');
background-repeat: no-repeat;
background-attachment: fixed;
background-size: cover;
min-height: 200vh;
margin: 0;
padding: 0;
}
.header-container {
margin: 0;
opacity: 0.885;
}
.container {
padding: 10px;
background-color: #FFA1C9;
float: left;
width: 75%;
display: flex;
flex-direction: column;
}
nav {
background-color: #F94892;
margin: 0 50px 50px 50px;
border-radius: 5px;
transition: 0.3s;
}
nav:hover {
transform: scale(1.005);
transition: 0.3s;
}
nav li {
color: rgb(227, 118, 118);
text-align: center;
padding: 10px;
}
nav ul {
margin-top: 0;
}
nav a {
color: white;
font-family: 'Quicksand';
font-size: 20px;
}
.myHeader {
text-align: center;
background-color: #FFC4C4;
margin: 20px 20px 0 20px;
border-radius: 10px;
padding: 12px;
}
header h1>img {
width: 42%;
}
nav li {
margin: 0;
}
nav a {
color: #fff;
font-size: 20px;
font-weight: 700;
position: relative;
z-index: 0;
font-family: 'Quicksand';
}
nav a::before {
content: "";
position: absolute;
width: 0;
height: 15px;
background: rgb(182, 1, 32);
bottom: 0;
left: 0;
z-index: -1;
transition: 0.2s linear;
}
nav a:hover::before {
width: 100%;
}
.card {
background-color: #FBE5E5;
box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
border-radius: 5px;
margin: 1.25em;
padding: 1.25em;
}
.card:hover {
transform: scale(1.0025);
transition: 0.2s;
position: relative;
}
.content-container>h2 {
margin: 10px;
}
/* text font-size */
h2 {
font-size: 2.25em;
color: rgb(212, 27, 58);
font-family: sans-serif;
font-weight: 700;
margin: 20px;
}
p {
font-size: 1.25em;
color: F94892;
}
h3 {
font-size: 1.25em;
color: rgb(212, 27, 58);
}
h1 {
margin: 0;
}
/* image */
.image-style {
text-align: center;
width: 100%;
max-height: 300%;
object-fit: cover;
object-position: center;
}
/* sticky navbar */
.sticky {
position: fixed;
top: 0;
width: 100%;
margin: 0;
transition: 0.3s;
transform: scale(1.0025);
}
.sticky li {
display: inline-block;
padding-left: 50px;
}
/* Add some top padding to the page content to prevent sudden quick movement (as the navigation bar gets a new position at the top of the page (position:fixed and top:0) */
.sticky+nav {
padding-top: 60px;
}
/* profile things */
.card-v2 {
background-color: #FBE5E5;
box-shadow: 0 4px 8px 0 rgba(255, 255, 255, 0.2);
border-radius: 5px;
margin: 1.25em;
padding: 1.25em;
}
.card-v2:hover {
transform: scale(1.0025);
transition: 0.2s;
box-shadow: 0 5px 10px 5px #F94892;
}
.profile {
background-color: #FFA1C9;
padding: 5px;
margin: 0;
float: right;
width: 25%
}
.profile img {
width: 200px;
}
.profile header {
text-align: center;
}
.profile-head {
display: inline;
}
#aside {
background-color: #FFA1C9;
margin: 0;
}
.card-v3 {
background-color: #FFC4C4;
border-radius: 5px;
margin: 1.25em;
padding: 1.25em;
}
.card-v3:hover {
box-shadow: 0 4px 8px 8px #efd6d6;
}
/* table */
.table-style {
text-align: center;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>My Problem</title>
</head>
<body>
<header class="header-container header-scroll">
<div class="myHeader">
<h1>
<img src="/Website/Images/Spy_×_Family_logo.png" alt="header">
</h1>
</div>
<nav class="myNav">
<ul>
<li><a href='#home'>Home</a></li>
<li><a href='#about'>About<a/></li>
<li><a href='#other'>Other</a></li>
</ul>
</nav>
</header>
<main>
<div class="container">
<article id="home" class="content-container-column card ">
<h2>Header 2</h2>
<img src="/Website/Images/3774625814.jpg" class="image-style" alt="">
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Eum architecto culpa ab enim tempora atque corporis nam rem, exercitationem quasi cumque et quam quisquam odio, labore fugit molestias, quo quod?</p>
<p>Lorem</p>
<h3>Header 3</h3>
<p>
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Architecto inventore nisi provident quasi reiciendis odit reprehenderit ut non, voluptatum perspiciatis blanditiis illo a! Rem, recusandae ab commodi provident ex praesentium.</p>
</article>
<article id="about" class="card content-container-column">
<h2>Header 2</h2>
<img src="/Website/Images/357396304.jpg" class="image-style" alt="">
<p>Lorem ipsum dolor sit, amet consectetur adipisicing elit. Excepturi expedita soluta nihil, praesentium perferendis cum rerum similique ab? Natus saepe molestias reiciendis voluptas voluptatibus consectetur adipisci praesentium asperiores deleniti
odio.</p>
</article>
<article id="other" class="card content-container-column">
<h2>Header 2</h2>
<img src="/Website/Images/spy-x-family-yor-forger.gif" class="image-style" alt="">
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Dolores tempora doloribus dicta quibusdam, corrupti quam maiores laboriosam quo voluptatum autem ea ad quaerat id suscipit magnam unde cupiditate, voluptates harum.</p>
</article>
</div>
<aside id="aside" class="profile">
<article class="card-v2">
<header class="profile-head">
<h2>About Me</h2>
<figure class="card-v3">
<img src="/Website/Images/Dwiki_Yulian.jpg" alt="">
</figure>
</header>
<section>
<table class="table-style">
<tr>
<th>Name:</th>
<td></td>
</tr>
<tr>
<th>Tempat, tanggal lahir:</th>
<td></td>
</tr>
<tr>
<th>Alamat:</th>
<td></td>
</tr>
<tr>
<th>Agama:</th>
<td></td>
</tr>
<tr>
</tr>
</table>
</section>
</article>
</aside>
</main>
<script src="muscle.js"></script>
</body>
</html>
If anything is missing from the snippet, you can check my jsfiddle here

What you're experiencing is something referred to as The Stacking Context which, if you think about it from a top-down perspective, is how elements are rendered in the browser. To solve this, you can set the parent element -- in this case the header-container -- to position: relative; and give it a z-index of 1 to override the default of 0. That will elevate it above the card which is using the default of 0 even when hovered.
Here's another good explanation for it as well: https://www.joshwcomeau.com/css/stacking-contexts/
window.onscroll = function() {
myFunction()
};
var navbar = document.querySelector(".myNav");
var sticky = navbar.offsetTop;
function myFunction() {
if (window.pageYOffset >= sticky) {
navbar.classList.add("sticky")
} else {
navbar.classList.remove("sticky");
}
}
#import url('https://fonts.googleapis.com/css2?family=Quicksand:wght#400;500;700&display=swap');
* {
text-decoration: none;
box-sizing: border-box;
font-family: sans-serif;
}
body {
background-image: url('/Website/Images/SPY_X_FAMILY.jpg');
background-repeat: no-repeat;
background-attachment: fixed;
background-size: cover;
min-height: 200vh;
margin: 0;
padding: 0;
}
.header-container {
margin: 0;
opacity: 0.885;
position: relative;
z-index: 1;
}
.container {
padding: 10px;
background-color: #FFA1C9;
float: left;
width: 75%;
display: flex;
flex-direction: column;
}
nav {
background-color: #F94892;
margin: 0 50px 50px 50px;
border-radius: 5px;
transition: 0.3s;
z-index: 2;
}
nav:hover {
transform: scale(1.005);
transition: 0.3s;
}
nav li {
color: rgb(227, 118, 118);
text-align: center;
padding: 10px;
}
nav ul {
margin-top: 0;
}
nav a {
color: white;
font-family: 'Quicksand';
font-size: 20px;
}
.myHeader {
text-align: center;
background-color: #FFC4C4;
margin: 20px 20px 0 20px;
border-radius: 10px;
padding: 12px;
}
header h1>img {
width: 42%;
}
nav li {
margin: 0;
}
nav a {
color: #fff;
font-size: 20px;
font-weight: 700;
position: relative;
z-index: 0;
font-family: 'Quicksand';
}
nav a::before {
content: "";
position: absolute;
width: 0;
height: 15px;
background: rgb(182, 1, 32);
bottom: 0;
left: 0;
z-index: -1;
transition: 0.2s linear;
}
nav a:hover::before {
width: 100%;
}
.card {
background-color: #FBE5E5;
box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
border-radius: 5px;
margin: 1.25em;
padding: 1.25em;
transition: 0.2s;
}
.card:hover {
transform: scale(1.0025);
transition: 0.2s;
}
.content-container>h2 {
margin: 10px;
}
/* text font-size */
h2 {
font-size: 2.25em;
color: rgb(212, 27, 58);
font-family: sans-serif;
font-weight: 700;
margin: 20px;
}
p {
font-size: 1.25em;
color: F94892;
}
h3 {
font-size: 1.25em;
color: rgb(212, 27, 58);
}
h1 {
margin: 0;
}
/* image */
.image-style {
text-align: center;
width: 100%;
max-height: 300%;
object-fit: cover;
object-position: center;
}
/* sticky navbar */
.sticky {
position: fixed;
top: 0;
width: 100%;
margin: 0;
transition: 0.3s;
transform: scale(1.0025);
z-index: 1;
}
.sticky li {
display: inline-block;
padding-left: 50px;
}
/* Add some top padding to the page content to prevent sudden quick movement (as the navigation bar gets a new position at the top of the page (position:fixed and top:0) */
.sticky+nav {
padding-top: 60px;
}
/* profile things */
.card-v2 {
background-color: #FBE5E5;
box-shadow: 0 4px 8px 0 rgba(255, 255, 255, 0.2);
border-radius: 5px;
margin: 1.25em;
padding: 1.25em;
z-index: 0;
}
.card-v2:hover {
transform: scale(1.0025);
transition: 0.2s;
box-shadow: 0 5px 10px 5px #F94892;
}
.profile {
background-color: #FFA1C9;
padding: 5px;
margin: 0;
float: right;
width: 25%
}
.profile img {
width: 200px;
}
.profile header {
text-align: center;
}
.profile-head {
display: inline;
}
#aside {
background-color: #FFA1C9;
margin: 0;
}
.card-v3 {
background-color: #FFC4C4;
border-radius: 5px;
margin: 1.25em;
padding: 1.25em;
z-index: 0;
}
.card-v3:hover {
box-shadow: 0 4px 8px 8px #efd6d6;
}
/* table */
.table-style {
text-align: center;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>My Problem</title>
</head>
<body>
<header class="header-container header-scroll">
<div class="myHeader">
<h1>
<img src="/Website/Images/Spy_×_Family_logo.png" alt="header">
</h1>
</div>
<nav class="myNav">
<ul>
<li><a href='#home'>Home</a></li>
<li><a href='#about'>About</a>a></li>
<li><a href='#other'>Other</a></li>
</ul>
</nav>
</header>
<main>
<div class="container">
<article id="home" class="content-container-column card ">
<h2>Header 2</h2>
<img src="/Website/Images/3774625814.jpg" class="image-style" alt="">
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Eum architecto culpa ab enim tempora atque corporis nam rem, exercitationem quasi cumque et quam quisquam odio, labore fugit molestias, quo quod?</p>
<p>Lorem</p>
<h3>Header 3</h3>
<p>
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Architecto inventore nisi provident quasi reiciendis odit reprehenderit ut non, voluptatum perspiciatis blanditiis illo a! Rem, recusandae ab commodi provident ex praesentium.</p>
</article>
<article id="about" class="card content-container-column">
<h2>Header 2</h2>
<img src="/Website/Images/357396304.jpg" class="image-style" alt="">
<p>Lorem ipsum dolor sit, amet consectetur adipisicing elit. Excepturi expedita soluta nihil, praesentium perferendis cum rerum similique ab? Natus saepe molestias reiciendis voluptas voluptatibus consectetur adipisci praesentium asperiores deleniti
odio.
</p>
</article>
<article id="other" class="card content-container-column">
<h2>Header 2</h2>
<img src="/Website/Images/spy-x-family-yor-forger.gif" class="image-style" alt="">
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Dolores tempora doloribus dicta quibusdam, corrupti quam maiores laboriosam quo voluptatum autem ea ad quaerat id suscipit magnam unde cupiditate, voluptates harum.</p>
</article>
</div>
<aside id="aside" class="profile">
<article class="card-v2">
<header class="profile-head">
<h2>About Me</h2>
<figure class="card-v3">
<img src="/Website/Images/Dwiki_Yulian.jpg" alt="">
</figure>
</header>
<section>
<table class="table-style">
<tr>
<th>Name:</th>
<td></td>
</tr>
<tr>
<th>Tempat, tanggal lahir:</th>
<td></td>
</tr>
<tr>
<th>Alamat:</th>
<td></td>
</tr>
<tr>
<th>Agama:</th>
<td></td>
</tr>
<tr>
</tr>
</table>
</section>
</article>
</aside>
</main>
<script src="muscle.js"></script>
</body>
</html>

try to set the z-index of the nav to 100
nav {
z-index: 100;
}

HTML Div takes up space while hidden

I have a problem. I made the following tabbedPage, but the hidden content still takes up space. Here is the code:
let tabHeader = document.getElementsByClassName("tabbedpage-header")[0];
let tabIndicator = document.getElementsByClassName("tabbedpage-indicator")[0];
let tabContent = document.getElementsByClassName("tabbedpage-content")[0];
let tabsPane = tabHeader.getElementsByTagName("div");
for (let i = 0; i < tabsPane.length; i++) {
tabsPane[i].addEventListener("click", function() {
tabHeader.getElementsByClassName("active")[0].classList.remove("active");
tabsPane[i].classList.add("active");
tabContent.getElementsByClassName("active")[0].classList.remove("active");
tabContent.getElementsByTagName("div")[i].classList.add("active");
tabIndicator.style.left = `calc(calc(100% / 2) * ${i})`;
});
}
/*--------------General----------------*/
body {
font-family: Arial;
}
.container {
width: 100%;
max-width: 1300px;
margin: 0 auto;
}
/*-------------------------------------*/
/*-------------TabbedPage---------------*/
.tabbedpage {
padding: 20px 0px;
}
.tabbedpage .tabbedpage-header {
height: 60px;
display: flex;
align-items: center;
}
.tabbedpage .tabbedpage-header>div {
width: calc(100% / 2);
text-align: center;
color: #888;
font-weight: 600;
cursor: pointer;
font-size: 20px;
text-transform: uppercase;
outline: none;
}
.tabbedpage .tabbedpage-header>div>i {
display: block;
margin-bottom: 5px;
}
.tabbedpage .tabbedpage-header>div.active {
color: #d81e05;
display: block;
}
.tabbedpage .tabbedpage-indicator {
position: relative;
width: calc(100% / 2);
height: 5px;
background: #d81e05;
left: 0px;
border-radius: 5px;
transition: all 500ms ease-in-out;
}
.tabbedpage .tabbedpage-content {
position: relative;
height: calc(100% - 60px);
padding: 10px 5px;
}
.tabbedpage .tabbedpage-content>div {
width: 100%;
top: 0;
left: 0;
opacity: 0;
transition: opacity 500ms ease-in-out 0ms, transform 500ms ease-in-out 0ms;
}
.tabbedpage .tabbedpage-content>div.active {
opacity: 1;
}
/*--------------------------------------*/
/*---------------Footer-----------------*/
footer {
width: 100%;
}
footer .red-bar {
display: flex;
align-items: center;
background: #d81e05;
height: 120px;
}
footer .red-bar .content {
display: flex;
align-items: center;
justify-content: flex-end;
}
/*------------------------------------------*/
<div class="container">
<div class="tabbedpage">
<div class="tabbedpage-header">
<div class="active">
statistics
</div>
<div>
user management
</div>
</div>
<div class="tabbedpage-indicator"></div>
<div class="tabbedpage-content">
<div class="active">
<h2>This is statistics section</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Error neque saepe commodi blanditiis fugiat nisi aliquam ratione porro quibusdam in, eveniet accusantium cumque. Dolore officia reprehenderit perferendis quod libero omnis.</p>
</div>
<div>
<h2>This is the user management section</h2>
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Modi minus exercitationem vero, id autem fugit assumenda a molestiae numquam at, quisquam cumque. Labore eligendi perspiciatis quia incidunt quaerat ut ducimus?</p>
</div>
</div>
</div>
</div>
<footer>
<div class="red-bar">
<div class="container content">
<p> Bel nu ons contact center <br> <b>023 751 06 06</b> </p>
</div>
</div>
</footer>
Now the TabbedPage is working the way I want, except that the content of a tab always uses space while not being showed. I can fix it by setting position: absolute;, but then the content goes trough the footer, which is also not allowed. So how can I remove the space that a hidden tab uses, while not going trough the footer?

You should use display instead of opacity.
But you should also set div to display: block; in div.active as below:
.tabbedpage .tabbedpage-content>div.active, .tabbedpage .tabbedpage-content>div.active div {
display: block; /* show it */
}
Pay attention that if you want to set div into div.active with a different displaythan you need to add !important to make sure that it will be taken correctly.
You also need to change some js in your for loop as below:
/** IF to point to the right div **/
if(tabsPane[i].className.match(/\bstat\b/)){
document.getElementById("stat").classList.add('active');
document.getElementById("userManagement").classList.remove('active');
}else if(tabsPane[i].className.match(/\buserManagement\b/)){
document.getElementById("userManagement").classList.add('active');
document.getElementById("stat").classList.remove('active');
}
And to make it works I was adding classes and id such as stat and userManagement because it was not identifying correctly the div anymore.
DEMO (Simple example):
let tabHeader = document.getElementsByClassName("tabbedpage-header")[0];
let tabIndicator = document.getElementsByClassName("tabbedpage-indicator")[0];
let tabContent = document.getElementsByClassName("tabbedpage-content")[0];
let tabsPane = tabHeader.getElementsByTagName("div");
for (let i = 0; i < tabsPane.length; i++) {
tabsPane[i].addEventListener("click", function() {
tabHeader.getElementsByClassName("active")[0].classList.remove("active");
tabsPane[i].classList.add("active");
/*tabContent.getElementsByClassName("active")[0].classList.remove("active");
tabContent.getElementsByTagName("div")[i].classList.add("active");*/
/** IF to point to the right div **/
if(tabsPane[i].className.match(/\bstat\b/)){
document.getElementById("stat").classList.add('active');
document.getElementById("userManagement").classList.remove('active');
}else if(tabsPane[i].className.match(/\buserManagement\b/)){
document.getElementById("userManagement").classList.add('active');
document.getElementById("stat").classList.remove('active');
}
tabIndicator.style.left = `calc(calc(100% / 2) * ${i})`;
});
}
/*--------------General----------------*/
body {
font-family: Arial;
}
.container {
width: 100%;
max-width: 1300px;
margin: 0 auto;
}
/*-------------------------------------*/
/*-------------TabbedPage---------------*/
.tabbedpage {
padding: 20px 0px;
}
.tabbedpage .tabbedpage-header {
height: 60px;
display: flex;
align-items: center;
}
.tabbedpage .tabbedpage-header>div {
width: calc(100% / 2);
text-align: center;
color: #888;
font-weight: 600;
cursor: pointer;
font-size: 20px;
text-transform: uppercase;
outline: none;
}
.tabbedpage .tabbedpage-header>div>i {
display: block;
margin-bottom: 5px;
}
.tabbedpage .tabbedpage-header>div.active {
color: #d81e05;
display: block;
}
.tabbedpage .tabbedpage-indicator {
position: relative;
width: calc(100% / 2);
height: 5px;
background: #d81e05;
left: 0px;
border-radius: 5px;
transition: all 500ms ease-in-out;
}
.tabbedpage .tabbedpage-content {
position: relative;
height: calc(100% - 60px);
padding: 10px 5px;
}
.tabbedpage .tabbedpage-content>div {
width: 100%;
top: 0;
left: 0;
display: none; /* hide it */
transition: opacity 500ms ease-in-out 0ms, transform 500ms ease-in-out 0ms;
}
.tabbedpage .tabbedpage-content>div.active, .tabbedpage .tabbedpage-content>div.active div {
display: block; /* show it */
}
/*--------------------------------------*/
/*---------------Footer-----------------*/
footer {
width: 100%;
}
footer .red-bar {
display: flex;
align-items: center;
background: #d81e05;
height: 120px;
}
footer .red-bar .content {
display: flex;
align-items: center;
justify-content: flex-end;
}
/*------------------------------------------*/
<div class="container">
<div class="tabbedpage">
<div class="tabbedpage-header">
<div class="stat active">
statistics
</div>
<div class="userManagement">
user management
</div>
</div>
<div class="tabbedpage-indicator"></div>
<div class="tabbedpage-content">
<div id="stat" class="active">
<h2>This is statistics section</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Error neque saepe commodi blanditiis fugiat nisi aliquam ratione porro quibusdam in, eveniet accusantium cumque. Dolore officia reprehenderit perferendis quod libero omnis.</p>
<div>DIV IN DIV 2</div>
</div>
<div id="userManagement">
<h2>This is the user management section</h2>
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Modi minus exercitationem vero, id autem fugit assumenda a molestiae numquam at, quisquam cumque. Labore eligendi perspiciatis quia incidunt quaerat ut ducimus?</p>
</div>
</div>
</div>
</div>
<footer>
<div class="red-bar">
<div class="container content">
<p> Bel nu ons contact center <br> <b>023 751 06 06</b> </p>
</div>
</div>
</footer>
DEMO (Large example):
let tabHeader = document.getElementsByClassName("tabbedpage-header")[0];
let tabIndicator = document.getElementsByClassName("tabbedpage-indicator")[0];
let tabContent = document.getElementsByClassName("tabbedpage-content")[0];
let tabsPane = tabHeader.getElementsByTagName("div");
for (let i = 0; i < tabsPane.length; i++) {
tabsPane[i].addEventListener("click", function() {
tabHeader.getElementsByClassName("active")[0].classList.remove("active");
tabsPane[i].classList.add("active");
/*tabContent.getElementsByClassName("active")[0].classList.remove("active");
tabContent.getElementsByTagName("div")[i].classList.add("active");*/
/** IF to point to the right div **/
if(tabsPane[i].className.match(/\bstat\b/)){
document.getElementById("stat").classList.add('active');
document.getElementById("userManagement").classList.remove('active');
}else if(tabsPane[i].className.match(/\buserManagement\b/)){
document.getElementById("userManagement").classList.add('active');
document.getElementById("stat").classList.remove('active');
}
tabIndicator.style.left = `calc(calc(100% / 2) * ${i})`;
});
}
/*--------------General----------------*/
body {
font-family: Arial;
}
.container {
width: 100%;
max-width: 1300px;
margin: 0 auto;
}
/*-------------------------------------*/
/*-------------TabbedPage---------------*/
.tabbedpage {
padding: 20px 0px;
}
.tabbedpage .tabbedpage-header {
height: 60px;
display: flex;
align-items: center;
}
.tabbedpage .tabbedpage-header>div {
width: calc(100% / 2);
text-align: center;
color: #888;
font-weight: 600;
cursor: pointer;
font-size: 20px;
text-transform: uppercase;
outline: none;
}
.tabbedpage .tabbedpage-header>div>i {
display: block;
margin-bottom: 5px;
}
.tabbedpage .tabbedpage-header>div.active {
color: #d81e05;
display: block;
}
.tabbedpage .tabbedpage-indicator {
position: relative;
width: calc(100% / 2);
height: 5px;
background: #d81e05;
left: 0px;
border-radius: 5px;
transition: all 500ms ease-in-out;
}
.tabbedpage .tabbedpage-content {
position: relative;
height: calc(100% - 60px);
padding: 10px 5px;
}
.tabbedpage .tabbedpage-content>div {
width: 100%;
top: 0;
left: 0;
display: none; /* hide it */
transition: opacity 500ms ease-in-out 0ms, transform 500ms ease-in-out 0ms;
}
.tabbedpage .tabbedpage-content>div.active, .tabbedpage .tabbedpage-content>div.active div {
display: block; /* show it */
}
/*--------------------------------------*/
/*-------------Statistics---------------*/
.activity-24h-title {
color: #000000;
font-size: 30px;
font-weight: bold;
}
.activity-24h {
width: 100%;
height: 125px;
background-color: #F6F6F6;
display: flex !important; /** Add !important **/
align-items: center;
justify-content: center;
}
.activity-24h .stat-frame {
position: relative;
width:calc(100% / 5 - (4 * 2px));
display: flex !important; /** Add !important **/
flex-direction: column
}
.activity-24h .stat-frame-title {
color: #000000;
font-size: 22px;
font-weight: bold;
text-align: center;
padding-bottom: 15px;
}
.activity-24h .stat-frame-value {
color: #d81e05;
font-size: 42px;
font-weight: bold;
width: 100%;
text-align: center;
}
.activity-24h .seperation-border {
width: 2px;
height: 80%;
background-color: #C4C4C4;
}
/*--------------------------------------*/
/*---------------Footer-----------------*/
footer {
width: 100%;
}
footer .red-bar {
display: flex;
align-items: center;
background: #d81e05;
height: 120px;
}
footer .red-bar .content {
display: flex;
align-items: center;
justify-content: flex-end;
}
<div class="tabbedpage">
<div class="tabbedpage-header">
<div class="stat active">
Statistieken
</div>
<div class="userManagement">
Gebruikersbeheer
</div>
</div>
<div class="tabbedpage-indicator"></div>
<div class="tabbedpage-content">
<div id="stat" class="active">
<span class="activity-24h-title">Afgelopen 24 uur</span>
<div class="activity-24h">
<div class="stat-frame">
<span class="stat-frame-title">Nieuwe gebruikers</span>
<span class="stat-frame-value">513</span>
</div>
<div class="seperation-border"></div>
<div class="stat-frame">
<span class="stat-frame-title">Actieve gebruikers</span>
<span class="stat-frame-value">1054</span>
</div>
<div class="seperation-border"></div>
<div class="stat-frame">
<span class="stat-frame-title">Matches</span>
<span class="stat-frame-value">1577</span>
</div>
<div class="seperation-border"></div>
<div class="stat-frame">
<span class="stat-frame-title">Gerapporteerd</span>
<span class="stat-frame-value">33</span>
</div>
<div class="seperation-border"></div>
<div class="stat-frame">
<span class="stat-frame-title">Geblokkeerd</span>
<span class="stat-frame-value">9</span>
</div>
</div>
</div>
<div id="userManagement">
<h2>This is about section</h2>
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Modi minus exercitationem vero, id autem fugit assumenda a molestiae numquam at, quisquam cumque. Labore eligendi perspiciatis quia incidunt quaerat ut ducimus?</p>
</div>
</div>
</div>
<footer>
<div class="red-bar">
<div class="container content">
<p> Bel nu ons contact center <br> <b>023 751 06 06</b> </p>
</div>
</div>
</footer>

You can achieve that by using display: none and display: block instead of opacity: 0 and opacity: 1 to hide the inactive element:
let tabHeader = document.getElementsByClassName("tabbedpage-header")[0];
let tabIndicator = document.getElementsByClassName("tabbedpage-indicator")[0];
let tabContent = document.getElementsByClassName("tabbedpage-content")[0];
let tabsPane = tabHeader.getElementsByTagName("div");
for (let i = 0; i < tabsPane.length; i++) {
tabsPane[i].addEventListener("click", function() {
tabHeader.getElementsByClassName("active")[0].classList.remove("active");
tabsPane[i].classList.add("active");
tabContent.getElementsByClassName("active")[0].classList.remove("active");
tabContent.getElementsByTagName("div")[i].classList.add("active");
tabIndicator.style.left = `calc(calc(100% / 2) * ${i})`;
});
}
/*--------------General----------------*/
body {
font-family: Arial;
}
.container {
width: 100%;
max-width: 1300px;
margin: 0 auto;
}
/*-------------------------------------*/
/*-------------TabbedPage---------------*/
.tabbedpage {
padding: 20px 0px;
}
.tabbedpage .tabbedpage-header {
height: 60px;
display: flex;
align-items: center;
}
.tabbedpage .tabbedpage-header>div {
width: calc(100% / 2);
text-align: center;
color: #888;
font-weight: 600;
cursor: pointer;
font-size: 20px;
text-transform: uppercase;
outline: none;
}
.tabbedpage .tabbedpage-header>div>i {
display: block;
margin-bottom: 5px;
}
.tabbedpage .tabbedpage-header>div.active {
color: #d81e05;
display: block;
}
.tabbedpage .tabbedpage-indicator {
position: relative;
width: calc(100% / 2);
height: 5px;
background: #d81e05;
left: 0px;
border-radius: 5px;
transition: all 500ms ease-in-out;
}
.tabbedpage .tabbedpage-content {
position: relative;
height: calc(100% - 60px);
padding: 10px 5px;
}
.tabbedpage .tabbedpage-content>div {
width: 100%;
top: 0;
left: 0;
display: none; /* hide it */
transition: opacity 500ms ease-in-out 0ms, transform 500ms ease-in-out 0ms;
}
.tabbedpage .tabbedpage-content>div.active {
display: block; /* show it */
}
/*--------------------------------------*/
/*---------------Footer-----------------*/
footer {
width: 100%;
}
footer .red-bar {
display: flex;
align-items: center;
background: #d81e05;
height: 120px;
}
footer .red-bar .content {
display: flex;
align-items: center;
justify-content: flex-end;
}
/*------------------------------------------*/
<div class="container">
<div class="tabbedpage">
<div class="tabbedpage-header">
<div class="active">
statistics
</div>
<div>
user management
</div>
</div>
<div class="tabbedpage-indicator"></div>
<div class="tabbedpage-content">
<div class="active">
<h2>This is statistics section</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Error neque saepe commodi blanditiis fugiat nisi aliquam ratione porro quibusdam in, eveniet accusantium cumque. Dolore officia reprehenderit perferendis quod libero omnis.</p>
</div>
<div>
<h2>This is the user management section</h2>
<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Modi minus exercitationem vero, id autem fugit assumenda a molestiae numquam at, quisquam cumque. Labore eligendi perspiciatis quia incidunt quaerat ut ducimus?</p>
</div>
</div>
</div>
</div>
<footer>
<div class="red-bar">
<div class="container content">
<p> Bel nu ons contact center <br> <b>023 751 06 06</b> </p>
</div>
</div>
</footer>

You can use document.write() to edit the document so you can remove add the div when required. Example:
function runcode(){
document.write("<div> hi </div>")
}
#button{
background-color: red;
padding: 15px 32px;
}
#button:hover{
background-color: pink;
}
<button onclick="runcode()" id="button">replace with a div with hi inside</button>

I think you should be using display instead of opacity, just as #MaxiGui wrote. You can be a bit fancy too, and create a tag for it:
invisible {
display:none;
}

As a quick workaround you can modify footer style as following.
footer {
width: 100%;
position: fixed;
left: 0;
bottom: 0;
}

Why can't I set the header background to a hex value?

So originally I wanted to set the header background to red for two seconds when one of the nav buttons was clicked. Now I want to change it to a random color for two seconds every time a nav button is clicked. So I created a random hex value. but when I try to set it using
header.style.background = hexColor;
It won't work?
header.style.background = 'red';
this will work, or if hexColor = 'red' will work. I can even log hexColor and see the hex value. What's the issue?
const navLinks = document.querySelectorAll('.nav-links .link');
const linksArray = Array.from(document.querySelectorAll('.links a'));
const header = document.querySelector('header');
for (var i = 0; i < navLinks.length; i++) {
navLinks[i].addEventListener('click', changeColor);
}
for (var i = 0; i < linksArray.length; i++) {
linksArray[i].addEventListener('click', shuffle);
}
function changeColor() {
let hexArray = [0, 1, 2, 3, 4, 5, 6, 'A', 'B', 'C', 'D', 'E', 'F'];
let hexColor = '#';
for(let i = 0; i <= 6; i++) {
let random = Math.floor(Math.random()*hexArray.length);
hexColor += hexArray[random];
}
header.style.background = hexColor;
setTimeout(function() {
header.style.backgroundImage = 'url(img/canada.jpeg)';
}, 2000);
}
function shuffle() { // Fisher-Yates shuffle algorithm
for (let i = linksArray.length - 1; i > 0; i--) {
let j = Math.floor(Math.random() * (i + 1)); // random index from 0 to i
[linksArray[i].innerHTML, linksArray[j].innerHTML] = [linksArray[j].innerHTML, linksArray[i].innerHTML]; // swap elements
}
}
html, body {
margin: 0;
padding: 0;
}
body {
font-family: 'Verdana';
box-sizing: border-box;
color: #63889b;
}
/** {
outline: 1px solid red;
}*/
/*------NAV-----*/
nav {
display: flex;
justify-content: space-between;
font-size: 1.8rem;
padding: 25px 0;
position: fixed;
background-color: #fff;
width: 100%;
top: 0;
left: 0;
right: 0;
z-index: 10;
}
.brand, .nav-links {
display: flex;
align-items: center;
}
.brand {
margin-left: 6%;
}
.logo {
max-width: 70px;
max-height: 45px;
margin-right: 25px;
}
.nav-links {
position: relative;
margin-right: 6%;
}
.nav-links .link {
text-transform: uppercase;
margin-right: 20px;
cursor: pointer;
transition: all .2s ease;
}
.nav-links .link:hover {
color: #014263;
}
/*-----HEADER-----*/
header {
margin-top: 92px;
background-image: url(img/canada.jpeg);
/*background-position: center;
background-size: cover;*/
padding-top: 7%;
padding-bottom: 25%;
}
.header-info {
color: #fff;
font-size: 1.5rem;
width: 26%;
background-color: rgba(0,0,0,0.6);
padding: 25px 0 25px 55px;
margin-left: 10%;
}
header p {
margin: 8px;
}
/*-----MAIN-----*/
main {
display: flex;
background-color: #fff;
}
.col {
flex-basis: 33.33%;
padding: 50px 0;
}
.col p {
width: 65%;
font-size: 1.25rem;
text-align: center;
margin-left: auto;
margin-right: auto;
}
.col img {
display: block;
margin: 0 auto;
}
.col-3 img {
width: 280px;
height: 155px;
}
.col-3 img, .col-3 h3, .col-3 p {
position: relative;
top: -8px;
}
.col-2 img, .col-2 h3, .col-2 p {
position: relative;
top: 30px;
}
.col-1 {
margin-left: 7%;
}
.col-3 {
margin-right: 7%;
}
h3 {
text-align: center;
}
/*------FOOTER-----*/
footer {
font-family: 'Helvetica';
background-color: #63889b;
display: flex;
justify-content: space-between;
color: #fff;
padding-bottom: 30px;
}
.internal-links {
padding-left: 20%;
font-size: 1.5rem;
}
a {
text-decoration: none;
margin:2px 0;
color: #fff;
cursor: pointer;
}
.internal-links h4 {
text-decoration: underline;
text-align: center;
margin-bottom: 8px;
margin-top: 30PX;
color: #fff;
}
.links {
font-size: 1.2rem;
display: flex;
flex-direction: column;
}
.form-wrap {
padding-top: 30px;
display: flex;
align-items: flex-end;
flex-basis: 50%;
}
form {
margin: 0 auto;
display: flex;
flex-direction: column;
width: 80%;
}
input {
border: none;
outline: none;
font-size: 1.6rem;
}
label {
font-size: 1.3rem;
padding: 3px 0;
}
button {
margin-top: 20px;
border: 1px solid #fff;
width: 50%;
font-size: 1.3rem;
background-color: #1090d1;
align-self: flex-end;
color: #fff;
padding: 4px 30px;
}
body {
background-color: rgba(0,0,0,0.6);
position: absolute;
left: 0;
right: 0;
bottom: 0;
top: 0;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Chapman Automotive Skills Assessment</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<nav>
<div class="brand">
<img src="img/Logo.png" alt="logo" class="logo">
<div class="comp-name">CHAPMAN</div>
</div>
<div class="nav-links">
<div class="link">Home</div>
<div class="link">Sales</div>
<div class="link">Blog</div>
<div class="link">Login</div>
</div>
</nav>
<header>
<div class="header-info">
<p>We are a company that does stuff.</p>
<p>Car and web stuff.</p>
</div>
</header>
<main>
<div class="col col-1">
<img src="img/car1.jpg" alt="car1">
<h3>Some Header</h3>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo tempore quia enim quod, perferendis illum quae id, natus dolores temporibus. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Obcaecati, rem. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Necessitatibus tenetur mollitia officiis laudantium dolore ipsa.</p>
</div>
<div class="col col-2">
<img src="img/car2.jpg" alt="car2">
<h3>More Stuff</h3>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo tempore quia enim quod, perferendis illum quae id, natus dolores temporibus. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Illo, dolor. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Perspiciatis, neque. Corporis quisquam eligendi libero omnis.</p>
</div>
<div class="col col-3">
<img src="img/car3.jpg" alt="car3">
<h3>Last Column</h3>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo tempore quia enim quod, perferendis illum quae id, natus dolores temporibus. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse, ipsa. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quod quae, nihil error delectus voluptatum deserunt.</p>
</div>
</main>
<footer id="footer">
<div class="internal-links">
<h4>Internal Links</h4>
<div class="links">
Page One
Another Page
Sales Page
Page Three
Keep Going
Last One
Just Kidding
</div>
</div>
<div class="form-wrap">
<form>
<label for="Name">Name</label>
<input type="text" id="Name">
<label for="Name">Address</label>
<input type="text" id="Address">
<label for="Name">City</label>
<input type="text" id="City">
<button type="submit">Submit Form</button>
</form>
<div class="dialog-wrap">
<dialog close>
<div class="name-field">Name:<span class="name">Seth</span></div>
<div class="name-field">Address:<span class="address">1013 N Arvada</span></div>
<div class="name-field">City:<span class="city">Mesa</span></div>
</dialog>
</div>
</footer>
<script src="script.js"></script>
</body>
</html>

Inside your change color function you have a for loop that stops after 7 values are appended.
Change for loop to i < 6 or i <= 5.
const navLinks = document.querySelectorAll('.nav-links .link');
const linksArray = Array.from(document.querySelectorAll('.links a'));
const header = document.querySelector('header');
for (var i = 0; i < navLinks.length; i++) {
navLinks[i].addEventListener('click', changeColor);
}
for (var i = 0; i < linksArray.length; i++) {
linksArray[i].addEventListener('click', shuffle);
}
function changeColor() {
let hexArray = [0, 1, 2, 3, 4, 5, 6, 'A', 'B', 'C', 'D', 'E', 'F'];
let hexColor = '#';
for(let i = 0; i <= 5; i++) {
let random = Math.floor(Math.random()*hexArray.length);
hexColor += hexArray[random];
}
header.style.background = hexColor;
setTimeout(function() {
header.style.backgroundImage = 'url(img/canada.jpeg)';
}, 2000);
}
function shuffle() { // Fisher-Yates shuffle algorithm
for (let i = linksArray.length - 1; i > 0; i--) {
let j = Math.floor(Math.random() * (i + 1)); // random index from 0 to i
[linksArray[i].innerHTML, linksArray[j].innerHTML] = [linksArray[j].innerHTML, linksArray[i].innerHTML]; // swap elements
}
}
html, body {
margin: 0;
padding: 0;
}
body {
font-family: 'Verdana';
box-sizing: border-box;
color: #63889b;
}
/** {
outline: 1px solid red;
}*/
/*------NAV-----*/
nav {
display: flex;
justify-content: space-between;
font-size: 1.8rem;
padding: 25px 0;
position: fixed;
background-color: #fff;
width: 100%;
top: 0;
left: 0;
right: 0;
z-index: 10;
}
.brand, .nav-links {
display: flex;
align-items: center;
}
.brand {
margin-left: 6%;
}
.logo {
max-width: 70px;
max-height: 45px;
margin-right: 25px;
}
.nav-links {
position: relative;
margin-right: 6%;
}
.nav-links .link {
text-transform: uppercase;
margin-right: 20px;
cursor: pointer;
transition: all .2s ease;
}
.nav-links .link:hover {
color: #014263;
}
/*-----HEADER-----*/
header {
margin-top: 92px;
background-image: url(img/canada.jpeg);
/*background-position: center;
background-size: cover;*/
padding-top: 7%;
padding-bottom: 25%;
}
.header-info {
color: #fff;
font-size: 1.5rem;
width: 26%;
background-color: rgba(0,0,0,0.6);
padding: 25px 0 25px 55px;
margin-left: 10%;
}
header p {
margin: 8px;
}
/*-----MAIN-----*/
main {
display: flex;
background-color: #fff;
}
.col {
flex-basis: 33.33%;
padding: 50px 0;
}
.col p {
width: 65%;
font-size: 1.25rem;
text-align: center;
margin-left: auto;
margin-right: auto;
}
.col img {
display: block;
margin: 0 auto;
}
.col-3 img {
width: 280px;
height: 155px;
}
.col-3 img, .col-3 h3, .col-3 p {
position: relative;
top: -8px;
}
.col-2 img, .col-2 h3, .col-2 p {
position: relative;
top: 30px;
}
.col-1 {
margin-left: 7%;
}
.col-3 {
margin-right: 7%;
}
h3 {
text-align: center;
}
/*------FOOTER-----*/
footer {
font-family: 'Helvetica';
background-color: #63889b;
display: flex;
justify-content: space-between;
color: #fff;
padding-bottom: 30px;
}
.internal-links {
padding-left: 20%;
font-size: 1.5rem;
}
a {
text-decoration: none;
margin:2px 0;
color: #fff;
cursor: pointer;
}
.internal-links h4 {
text-decoration: underline;
text-align: center;
margin-bottom: 8px;
margin-top: 30PX;
color: #fff;
}
.links {
font-size: 1.2rem;
display: flex;
flex-direction: column;
}
.form-wrap {
padding-top: 30px;
display: flex;
align-items: flex-end;
flex-basis: 50%;
}
form {
margin: 0 auto;
display: flex;
flex-direction: column;
width: 80%;
}
input {
border: none;
outline: none;
font-size: 1.6rem;
}
label {
font-size: 1.3rem;
padding: 3px 0;
}
button {
margin-top: 20px;
border: 1px solid #fff;
width: 50%;
font-size: 1.3rem;
background-color: #1090d1;
align-self: flex-end;
color: #fff;
padding: 4px 30px;
}
body {
background-color: rgba(0,0,0,0.6);
position: absolute;
left: 0;
right: 0;
bottom: 0;
top: 0;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Chapman Automotive Skills Assessment</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<nav>
<div class="brand">
<img src="img/Logo.png" alt="logo" class="logo">
<div class="comp-name">CHAPMAN</div>
</div>
<div class="nav-links">
<div class="link">Home</div>
<div class="link">Sales</div>
<div class="link">Blog</div>
<div class="link">Login</div>
</div>
</nav>
<header>
<div class="header-info">
<p>We are a company that does stuff.</p>
<p>Car and web stuff.</p>
</div>
</header>
<main>
<div class="col col-1">
<img src="img/car1.jpg" alt="car1">
<h3>Some Header</h3>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo tempore quia enim quod, perferendis illum quae id, natus dolores temporibus. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Obcaecati, rem. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Necessitatibus tenetur mollitia officiis laudantium dolore ipsa.</p>
</div>
<div class="col col-2">
<img src="img/car2.jpg" alt="car2">
<h3>More Stuff</h3>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo tempore quia enim quod, perferendis illum quae id, natus dolores temporibus. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Illo, dolor. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Perspiciatis, neque. Corporis quisquam eligendi libero omnis.</p>
</div>
<div class="col col-3">
<img src="img/car3.jpg" alt="car3">
<h3>Last Column</h3>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Explicabo tempore quia enim quod, perferendis illum quae id, natus dolores temporibus. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse, ipsa. Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quod quae, nihil error delectus voluptatum deserunt.</p>
</div>
</main>
<footer id="footer">
<div class="internal-links">
<h4>Internal Links</h4>
<div class="links">
Page One
Another Page
Sales Page
Page Three
Keep Going
Last One
Just Kidding
</div>
</div>
<div class="form-wrap">
<form>
<label for="Name">Name</label>
<input type="text" id="Name">
<label for="Name">Address</label>
<input type="text" id="Address">
<label for="Name">City</label>
<input type="text" id="City">
<button type="submit">Submit Form</button>
</form>
<div class="dialog-wrap">
<dialog close>
<div class="name-field">Name:<span class="name">Seth</span></div>
<div class="name-field">Address:<span class="address">1013 N Arvada</span></div>
<div class="name-field">City:<span class="city">Mesa</span></div>
</dialog>
</div>
</footer>
<script src="script.js"></script>
</body>
</html>

Use CSS3 transitions on the opacity property for tabbed content does not work

I am working on a simple tabbed content box in HTML5, CSS3 and jQuery.
It works fine except I have not been able to fade the content in gradually, using CSS transitions and opacity. Here is the code:
$("#filters_switch").on("click", "li", function() {
$('#filters_switch li').removeClass('tab_selected');
$(this).addClass('tab_selected');
$('#filters_content > div').removeClass('tab_selected');
$('#' + $(this).find('a').data('href')).addClass('tab_selected');
});
#filters_switch {
padding: 0 4px;
margin-top: 10px;
border-bottom: 1px solid #d0d0d0;
text-align: center;
}
#filters_switch li {
display: block;
float: left;
min-width: 200px;
padding: 0 1px;
margin-bottom: -1px;
}
#filters_switch li.tab_selected a {
color: #000;
background: #fff;
border-bottom: 1px solid #fff;
}
#filters_switch a {
display: block;
text-decoration: none;
padding: 3px 6px;
font-size: 12px;
font-weight: bold;
background: #f2f2f2;
color: #962b27;
border: 1px solid #d0d0d0;
border-radius: 8px 8px 0 0;
}
#filters_content .tab {
padding: 0 10px;
display: none;
opacity: 0;
-webkit-transition: opacity 0.5s;
-o-transition: opacity 0.5s;
transition: opacity 0.5s;
}
#filters_content .tab.tab_selected {
display: block;
opacity: 1;
}
#filters_content .tab h2 {
font-size: 18px;
font-weight: bold;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul id="filters_switch" class="tabnav clearfix">
<li id="filters_standard_link" class="tabnav_li tab_selected">
<a class="tabnavlink" href="#" data-href="filters_standard">Tab 1</a>
</li>
<li id="filters_advanced_link" class="tabnav_li">
<a class="tabnavlink" href="#" data-href="filters_advanced">Tab 2</a>
</li>
</ul>
<div id="filters_content" class="tabs">
<div id="filters_standard" data-id="filters_standard" class="tab tab_selected">
<h2>Lorem ipsum dolor sit amet</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
<div id="filters_advanced" data-id="filters_advanced" class="tab">
<h2>Esse odit sapiente odio deleniti</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
</div>
Since transitions can't be used on the display property, I have used it on the opacity, expecting the content to be firstly displayed, but with 0 opacity, then with opacity slowly brought to 1.
Yet, this does not happen. Why? How can I fix the problem?

As you said, you can't apply CSS transitions to display, so instead, try using .fadeIn() and .fadeOut() while absolutely positioning the tabs.
HIH
$("#filters_switch").on("click", "li", function() {
if(!$(this).hasClass('tab_selected')){
$(this).addClass('tab_selected').siblings('li').removeClass('tab_selected');
$('#' + $(this).find('a').data('href')).fadeIn('slow').siblings('div.tab').fadeOut('slow');
}
});
#filters_switch {
padding: 0 4px;
margin-top: 10px;
border-bottom: 1px solid #d0d0d0;
text-align: center;
}
#filters_switch li {
display: block;
float: left;
min-width: 200px;
padding: 0 1px;
margin-bottom: -1px;
}
#filters_switch li.tab_selected a {
color: #000;
background: #fff;
border-bottom: 1px solid #fff;
}
#filters_switch a {
display: block;
text-decoration: none;
padding: 3px 6px;
font-size: 12px;
font-weight: bold;
background: #f2f2f2;
color: #962b27;
border: 1px solid #d0d0d0;
border-radius: 8px 8px 0 0;
}
#filters_content .tab {
padding: 0 10px;
display: none;
position: absolute;
}
#filters_content .tab.tab_selected {
display: block;
//opacity: 1;
}
#filters_content .tab h2 {
font-size: 18px;
font-weight" bold;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul id="filters_switch" class="tabnav clearfix">
<li id="filters_standard_link" class="tabnav_li tab_selected">
<a class="tabnavlink" href="#" data-href="filters_standard">Tab 1</a>
</li>
<li id="filters_advanced_link" class="tabnav_li">
<a class="tabnavlink" href="#" data-href="filters_advanced">Tab 2</a>
</li>
</ul>
<div id="filters_content" class="tabs">
<div id="filters_standard" data-id="filters_standard" class="tab tab_selected">
<h2>Lorem ipsum dolor sit amet</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
<div id="filters_advanced" data-id="filters_advanced" class="tab">
<h2>Esse odit sapiente odio deleniti</h2>
<p>Lorem ipsum dol odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
</div>

You need to modify jQuery and css. with the use of fadeIn and fadeOut, you can achieve what you want
$("#filters_switch").on("click", "li", function() {
var toggleSection = $(this).attr('data-toggle');
$('.tabnav li').removeClass('tab_selected');
$(this).addClass('tab_selected');
$('#filters_content > div').fadeOut(250);
$("[data-tab="+toggleSection+"]").delay(300).fadeIn(250);
});
#filters_switch {
padding: 0 4px;
margin-top: 10px;
border-bottom: 1px solid #d0d0d0;
text-align: center;
}
#filters_switch li {
display: block;
float: left;
min-width: 200px;
padding: 0 1px;
margin-bottom: -1px;
}
#filters_switch li.tab_selected a {
color: #000;
background: #fff;
border-bottom: 1px solid #fff;
}
#filters_switch a {
display: block;
text-decoration: none;
padding: 3px 6px;
font-size: 12px;
font-weight: bold;
background: #f2f2f2;
color: #962b27;
border: 1px solid #d0d0d0;
border-radius: 8px 8px 0 0;
}
#filters_content .tab {
padding: 0 10px;
/* display: none; */
/* opacity: 0; */
/* -webkit-transition: opacity 0.5s;
-o-transition: opacity 0.5s;
transition: opacity 0.5s; */
}
#filters_content .tab.tab_selected {
display: block;
/* opacity: 1; */
}
#filters_content .tab h2 {
font-size: 18px;
font-weight:bold;
}
#filters_content > div {
display: none;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul id="filters_switch" class="tabnav clearfix">
<li id="filters_standard_link" class="tabnav_li tab_selected" data-toggle="section-one">
<a class="tabnavlink" href="#" data-href="filters_standard">Tab 1</a>
</li>
<li id="filters_advanced_link" class="tabnav_li" data-toggle="section-two">
<a class="tabnavlink" href="#" data-href="filters_advanced">Tab 2</a>
</li>
</ul>
<div id="filters_content" class="tabs">
<div id="filters_standard" data-id="filters_standard" data-tab="section-one" class="tab tab_selected">
<h2>Lorem ipsum dolor sit amet</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
<div id="filters_advanced" data-id="filters_advanced" class="tab" data-tab="section-two">
<h2>Esse odit sapiente odio deleniti</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
</div>
Working fiddle here

Transition doesn't get applied to certain properties including display property so you can use a workaround using, z-index, and position absolute, like the example..
$("#filters_switch").on("click", "li", function() {
$('#filters_switch li').removeClass('tab_selected');
$(this).addClass('tab_selected');
$('#filters_content > div').removeClass('tab_selected');
$('#' + $(this).find('a').data('href')).addClass('tab_selected');
});
#filters_switch {
padding: 0 4px;
margin-top: 10px;
border-bottom: 1px solid #d0d0d0;
text-align: center;
}
#filters_switch li {
display: block;
float: left;
min-width: 200px;
padding: 0 1px;
margin-bottom: -1px;
}
#filters_switch li.tab_selected a {
color: #000;
background: #fff;
border-bottom: 1px solid #fff;
}
#filters_switch a {
display: block;
text-decoration: none;
padding: 3px 6px;
font-size: 12px;
font-weight: bold;
background: #f2f2f2;
color: #962b27;
border: 1px solid #d0d0d0;
border-radius: 8px 8px 0 0;
}
#filters_content {
position:relative;
}
#filters_content .tab {
padding: 0 10px;
z-index: 0;
opacity: 0;
-webkit-transition: opacity 0.5s;
-o-transition: opacity 0.5s;
transition: opacity 0.5s;
position: absolute;
top: 0;
}
#filters_content .tab.tab_selected {
z-index: 1;
opacity: 1;
}
#filters_content .tab h2 {
font-size: 18px;
font-weight" bold;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul id="filters_switch" class="tabnav clearfix">
<li id="filters_standard_link" class="tabnav_li tab_selected">
<a class="tabnavlink" href="#" data-href="filters_standard">Tab 1</a>
</li>
<li id="filters_advanced_link" class="tabnav_li">
<a class="tabnavlink" href="#" data-href="filters_advanced">Tab 2</a>
</li>
</ul>
<div id="filters_content" class="tabs">
<div id="filters_standard" data-id="filters_standard" class="tab tab_selected">
<h2>Lorem ipsum dolor sit amet</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
<div id="filters_advanced" data-id="filters_advanced" class="tab">
<h2>Esse odit sapiente odio deleniti</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
</div>

Removed display:none from .tab and positioned them absolute.
$("#filters_switch").on("click", "li", function() {
$('#filters_switch li').removeClass('tab_selected');
$(this).addClass('tab_selected');
$('#filters_content > div').removeClass('tab_selected');
$('#' + $(this).find('a').data('href')).addClass('tab_selected');
});
#filters_switch {
padding: 0 4px;
margin-top: 10px;
border-bottom: 1px solid #d0d0d0;
text-align: center;
}
#filters_switch li {
display: block;
float: left;
min-width: 200px;
padding: 0 1px;
margin-bottom: -1px;
}
#filters_switch li.tab_selected a {
color: #000;
background: #fff;
border-bottom: 1px solid #fff;
}
#filters_switch a {
display: block;
text-decoration: none;
padding: 3px 6px;
font-size: 12px;
font-weight: bold;
background: #f2f2f2;
color: #962b27;
border: 1px solid #d0d0d0;
border-radius: 8px 8px 0 0;
}
#filters_content {
position: relative;
}
#filters_content .tab {
padding: 0 10px;
opacity: 0;
-webkit-transition: opacity 0.5s;
-o-transition: opacity 0.5s;
transition: opacity 0.5s;
position: absolute;
}
#filters_content .tab.tab_selected {
display: block;
opacity: 1;
}
#filters_content .tab h2 {
font-size: 18px;
font-weight" bold;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<ul id="filters_switch" class="tabnav clearfix">
<li id="filters_standard_link" class="tabnav_li tab_selected">
<a class="tabnavlink" href="#" data-href="filters_standard">Tab 1</a>
</li>
<li id="filters_advanced_link" class="tabnav_li">
<a class="tabnavlink" href="#" data-href="filters_advanced">Tab 2</a>
</li>
</ul>
<div id="filters_content" class="tabs">
<div id="filters_standard" data-id="filters_standard" class="tab tab_selected">
<h2>Lorem ipsum dolor sit amet</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
<div id="filters_advanced" data-id="filters_advanced" class="tab">
<h2>Esse odit sapiente odio deleniti</h2>
<p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse odit sapiente, odio deleniti asperiores iusto animi hic sint voluptate incidunt.</p>
</div>
</div>