Let's say banner is holding 200px height of the page and we want to calculate client's rest of the page height and hold restOfThePageDiv at same proportion all the time. Mostly we use something like that with using javascript (in this case jquery):
$( window ).resize(function() { var bannerHeight = $("#banner").height(); var restOfThePageHeight = $(window).height()-bannerHeight(); $("restOfThePageDiv").height(restOfThePageHeight); });
With css3 calc() ability we can create our page with using only css and html without using any kind of javascript code: