Develop Reference

Do you need to add constraints in html, js, and css for resizing to different screen sizes

I am pretty new to html, js, and css. I was wondering if just. like in IOS development where auto layout is needed for different screen sizes and/or orientations if this is the case for developing a website. I've looked around and seen things like margins and auto, but I'm not sure. Is there any specific links or videos one could suggest to understand this concept so that no matter how the screen size is the contents on board will adjust. Thank you.

use media queries like this :
#media only screen and (min-width: 1024px) and (max-width: 1025px) and (min-height: 1366px) and (max-height: 1367px) {
.header { width: 90%; }
}

How to detect screen resoluion without javascript?

In case i want to check user's device by its resolution(i.e 300x600px for mobile, 800x600px for tab, and 1024x768px for pc).
but, how can i get the user's screen resolution when their javascript is disabled?
or is there any other way to solve my problem?

You can use CSS media queries to apply CSS rules targeted at certain screen resolutions and orientations.

I dont think you need to create diffrent pages for eaxh reslolution juat use CSS media queries for adjust page according layout.
If you want diffrent page per resolution then you have to use some server side lib or function to detect browser resolution

#media should do it
By your specs:
#media (max-width: 799px) {
#import url("/uri/to/mobile.css");
}
#media (min-width: 800px) {
#import url("uri/to/tablet.css");
}
#media (min-width: 1024) {
#import url("/uri/to/desktop.css");
}

How to stop "tel:number" links from working on desktop / tablets

This must be very common.... I apologize, but can't find a working solution here...
I'm working on a site (retrofit) and it has responsive CSS such as:
/* Refecence from responsive.css
/* crank up to 5000px to support high res monitors and TV's */
#media only screen and (min-width: 1200px) and (max-width: 5000px)
/* Portrait tablet to landscape and desktop - BROWSER SIZE 2 */
#media only screen and (min-width: 991px) and (max-width: 1200px)
/* Landscape phone to portrait tablet - BROWSER SIZE 3 */
#media only screen and (min-width: 767px) and (max-width: 991px)
/* All Mobile Sizes (devices and browser) - BROWSER SIZE 4 */
#media only screen and (max-width: 767px)
/* Landscape phones and down - BROWSER SIZE 5 */
#media (max-width: 480px)
/* iphone portrait mode - BROWSER SIZE 6 */
#media (max-width: 320px)
I'm new to this, and done quite a bit of research, but I have a couple of questions:
I have the plan to have two blocks of HTML, one hidden, and use JS or CSS to hide the appropriate block based on user being on mobile device or not.
I wish to avoid useragent, as there are way too many. By default, Android no longer parses numbers as such (as per other posts) without the 'tel:'. I tested on Nexus 5. On the other hand Firefox asks for device to use on a 'tel: 'link.
Can I use my current #media CSS blocks? If so what about retina?
OR can useragent based JS be ok somehow?
Other options, I mean what do most people do???
Help is appreciated.

After more research I settled on a Javascript library isMobile.
https://github.com/kaimallea/isMobile
It seems that many use it, so I assume it would work.
My worry is that if a new device comes up, i have to continually update this library...

responsive tables in css

I am trying to make the following jsfiddle code work. Actually all is working fine, for server side i am using ColdFusion.
the values are appearing 6 in a row. the 6 is hard-coded in ColdFusion variables, so it splits the values in 6 and then next row.
Now i want to make this a responsive so it should work with tablets and mobile devices without much pain in the a****s
Here is the fiddle i had generated
http://jsfiddle.net/9arpxvga/
This needs a help in implementation of responsive design...
A Jquery, javascript solution will also work

You're going to be hard-pressed to find an objective solution to such a broad question. So, broadly: one of the many ways to implement responsive design is to write CSS media queries, targeting various screen sizes. Here's an example snippet taken from getskeleton.com (which might be worth checking out if you need a bare-bones responsive framework to get you started)
/* #Media Queries
================================================== */
/* Smaller than standard 960 (devices and browsers) */
#media only screen and (max-width: 959px) {}
/* Tablet Portrait size to standard 960 (devices and browsers) */
#media only screen and (min-width: 768px) and (max-width: 959px) {}
/* All Mobile Sizes (devices and browser) */
#media only screen and (max-width: 767px) {}
/* Mobile Landscape Size to Tablet Portrait (devices and browsers) */
#media only screen and (min-width: 480px) and (max-width: 767px) {}
/* Mobile Portrait Size to Mobile Landscape Size (devices and browsers) */
#media only screen and (max-width: 479px) {}
You'd just write new CSS (or override your css) for each of the screen sizes you're trying to target. (Nest your css within the brackets after each media screen). Hope that helps.

I want my font sizes to change responsively. Is javascript the best way?

If I hava all my font sizes in ems, and then use javascript to change the css rule determining font-size of the body (which will be in px) surely this will result in text that grows with a widening, percentage-based grid?
Apparently, changing css rules is tricky and doesn't support legacy versions of some browsers (guess which one), but if I embed my body rules right on the page, will that make things cross compliant?

you can use the font-size in em like font-size:1em or in % like font-size:5%
try to put the css in
#media screen and (min-width: 768px) and (max-width: 800px)
{ css }
according to device width like ipad and for the iphone you can change that
#media screen and (min-width: 320px) and (max-width: 480px)
{ here is css }
so that you able to see your design perfectly st these resolution