function getWindowHeight() { 
         var windowHeight = 0; 
         if (typeof(window.innerHeight) == 'number') { 
            windowHeight = window.innerHeight; 
         } 
         else { 
            if (document.documentElement && document.documentElement.clientHeight) { 
               windowHeight = document.documentElement.clientHeight; 
            } 
            else { 
               if (document.body && document.body.clientHeight) { 
                  windowHeight = document.body.clientHeight; 
               } 
            } 
         } 
         return windowHeight; 
      } 
      function setFooter() { 
         if (document.getElementById) { 
            var windowHeight = getWindowHeight(); 
            if (windowHeight > 0) { 
               var mainHeight = document.getElementById('main').offsetHeight; 
               var footerElement = document.getElementById('footer'); 
               var footerHeight  = footerElement.offsetHeight; 
               if (windowHeight - (mainHeight + footerHeight) >= 0) { 
                  footerElement.style.position = 'relative'; 
                  footerElement.style.top = (windowHeight - (mainHeight + footerHeight)) + 'px'; 
               } 
               else { 
                  footerElement.style.position = 'static'; 
               } 
            } 
         } 
      } 
      window.onload = function() { 
         setFooter(); 
      } 
      window.onresize = function() { 
         setFooter(); 
      }