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');
    });
});

Answer 2

One way to achieve this in some cases via just HTML and CSS is to have absolutely positioned div with it's top set to the 70px and every other direction set to 0px. Then every other side will adjust itself to the edges of the browser window.

For example:

<style type="text/css">
#fullscreen {
    background-color: #0000FF;
    position: absolute;
    top: 70px;
    left: 0px;
    right: 0px;
    bottom: 0px;
}
</style>

<div id="fullscreen">The Full Screen</div>