//检测username
    var isCheck = 0;   //检查检测后用户帐号的是否能使用
    function sendRequest(url)
    {
        http_request = false;
        if(window.XMLHttpRequest)
        {
            http_request = new XMLHttpRequest();
            if(http_request.overrideMimeType)
            {
                http_request.overrideMimeType("text/xml");
            }
        }
        else if (window.ActiveXObject)
        {
            try 
            {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            }
            catch(e)
            {
                try
                {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");              
                }
                catch(e){}
            }
        }
        if(!http_request)
        {
            window.alert("不能创建XMLHttpRequest对象实例.");
            return false;       
        }
        http_request.onreadystatechange = processRequest;
        http_request.open("GET", url, true);
        http_request.send(null);
    }

    function processRequest()
    {
        if (http_request.readyState == 4)
        {
            if (http_request.status == 200)
            {           
                document.getElementById("username_info").className = "SucceedMsg";
                var temp = http_request.responseText;//获取返回的信息
                var tv = temp.split(";");
                if(tv[0] == 1)
                {
                    isCheck = 1;
                }
                else
                {
                    isCheck = 0;
                    document.getElementById("username_info").className = "WarningMsg";
                }
                document.getElementById("username_info").innerHTML = tv[1] ;
            }
            else
            {
                alert("您所请求的页面有异常。");            
            }
        }
    }
	function checkUserNameFromDB(url)
    {
        if (document.regform.username.value=="")
        {
            document.getElementById("username_info").className = "WarningMsg";//default	WarningMsg	FailedMsg	SucceedMsg
            document.getElementById("username_info").innerHTML = "用户名不能为空！";
            return false;
        } 
        else
        {
		   sendRequest(url);
        }
    }