CSS Style switcher in JavaScript on an Asp .Net server

Question

I am trying to create a mobile website and can do it with just CSS, but the server master pages MUST be in their current locations, I am planning to use a Javascript "Style Switcher" to change the stylesheets but most mobile browsers don't have java support, so is there a way using java (or any other "language" that is either supported by mobile phones or can be run server-side) to run server-side that can also stop some of the page elements from loading (for mobile bandwidth issues) and change a few lines of the master code?

I was thinking of using this (with some edits): How to Use JavaScript to Change a Cascading Style Sheet (CSS) Dynamically

I cannot use PHP as our hosting provider will not install it.

I do not have Asp .Net access (as a user) but do have FTP access.

Answer 1

var isMobile = function() {
    var w = window.innerWidth || document.body.clientWidth;
    var o = 900;
    if(w < o) {
        return true;
    }
    else {
        return false;
    }
};

and an init func

var init = function(){
  if(!isMobile()){
    // all your desktop stuff goes here
    var desktopcss = document.createElement('link');
    desktopcss.rel = 'stylesheet';desktopcss.type = 'text/css';
    desktopcss.href='/desktop.css';
    document.getElementsByTagName('head')[0].appendChild(desktopcss);
  }
  else{
    // all your mobile stuff goes here
    var mobilecss= document.createElement('link');
    mobilecss.rel = 'stylesheet';mobilecss.type = 'text/css';
    mobilecss.href='/mobile.css';
    document.getElementsByTagName('head')[0].appendChild(mobilecss);
  }
};

and keep in mind that if you set something to

display:none;

via css, it will not be loaded and it will not be displayed!