function initAjax() {
	var ajax=false;
	//开始初始化XMLHttpRequest对象
	if(window.XMLHttpRequest){//Mozilla浏览器
	 ajax=new XMLHttpRequest();
	 if(ajax.overrideMimeType){//设置MIME类别
	   ajax.overrideMimeType("text/xml");
	 }
	}
	else if(window.ActiveXObject){//IE浏览器
		try {
			ajax = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try {
				ajax = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (E) {
				ajax = false;
			}
		}
	}
	if (!ajax && typeof XMLHttpRequest!='undefined') {
		ajax = new XMLHttpRequest();
		//window.alert("创建XMLHttp对象失败！");
		//return false;
	}
	return ajax;
}