//导航鼠标特效
function setNav(){
	var sitem = document.getElementsByClassName("top_pic");
	for (var i = 0; i< sitem.length; i++)
	{
		sitem[i].onmouseover = function(){this.style.filter = "alpha(Opacity=85)";}
		sitem[i].onmouseout = function(){this.style.filter = "alpha(Opacity=100)";}
	}
}

//获取class属性对象
document.getElementsByClassName = function(cl) {
	var retnode = [];
	var myclass = new RegExp('\\b'+cl+'\\b');
	var elem = this.getElementsByTagName('*');
	for (var j = 0; j < elem.length; j++) {
		var classes = elem[j].className;
		if (myclass.test(classes)) retnode.push(elem[j]);
	}
	return retnode;
}