//公用
var mainnav=$("main_nav");
var haschild=getElementsByClassName("haschild","a");

for(var i=0;i<haschild.length;i++){
	cleanWhitespace(haschild[i].parentNode);
	haschild[i].parentNode.onmouseover=function(){
		this.firstChild.nextSibling.style.display="block";
	}
	haschild[i].parentNode.onmouseout=function(){
		this.firstChild.nextSibling.style.display="none";
	}
}