function addLoadEvent(func) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	} else {
		window.onload = function() {
		oldonload();
		func();
		}
	}
}

function bottomFloatLayer(){
	var floatLayer = document.getElementById("floatLayer");
	rightBottomAd(floatLayer.offsetHeight);
}
function rightBottomAd(floatLayerHeight){
var floatLayer = document.getElementById("floatLayer");
//alert(document.documentElement.scrollTop);
floatLayer.style.top = document.documentElement.scrollTop+30+"px";//20是这个层的高度；
setTimeout(function(){rightBottomAd(floatLayerHeight);},50);
}

addLoadEvent(bottomFloatLayer);