Resize div on browser resize

Answer 1

Try this:

$(window).resize(function(){
  $('#fullscreen').height($(document).height() - ($('#div1').height() + $('#div2').height()) + 'px');
});

Updated Based On Comment:

I am using the jQuery in above code, you will have to download and include it in your page first.

Once you have downloaded and included in your page, then use this code:

$(function(){
    $(window).resize(function(){
      $('#fullscreen').height($(document).height() - ($('#div1').height() + $('#div2').height()) + 'px');
    });
});