window.onload = function(){
	pos();
	}
	
window.onresize = function(){
	pos();
	
}
function pos(){
	CH = document.documentElement.clientHeight;
	O = getElementsByClass(document, "div", "mainContainer");
	//alert(O.offsetHeight);
	if(CH > O.offsetHeight)
	{
			if( (CH - O.offsetHeight) > 74 ){O.style.marginTop = "37px";}
		    else {O.style.marginTop = (CH - O.offsetHeight)/2 + "px";}
		}
		else {
			O.style.marginTop = "0px";
			}
}