让IE支持getElementsByClassName

if (navigator.appName == 'Microsoft Internet Explorer') {
		document.getElementsByClassName = function() {
			var tTagName = "*";
			if (arguments.length > 1) {
				tTagName = arguments[1];
			}
			if (arguments.length > 2) {
				var pObj = arguments[2]
			} else {
				var pObj = document;
			}
			var objArr = pObj.getElementsByTagName(tTagName);
			var tRObj = new Array();
			for ( var i = 0; i < objArr.length; i++) {
				if (objArr[i].className == arguments[0]) {
					tRObj.push(objArr[i]);
				}
			}
			return tRObj;
		}
	}