function loginUser(){
            var msgw,msgh,bordercolor;
            msgw=300;//提示窗口的宽度
            msgh=200;//提示窗口的高度
            bordercolor="#336699";//提示窗口的边框颜色
            titlecolor="#99CCFF";//提示窗口的标题颜色
            
            var sWidth,sHeight;
            sWidth=document.body.offsetWidth;
            sHeight=document.body.offsetHeight;

            

            var bgObj=document.createElement("div");
            bgObj.setAttribute('id','bgDiv');
            bgObj.style.position="absolute";
            bgObj.style.top="0";
            bgObj.style.background="#777";
            bgObj.style.filter="progid:DXImageTransform.Microsoft.Alpha(style=3,opacity=25,finishOpacity=75";
            bgObj.style.opacity="0.6";
            bgObj.style.left="0";
            bgObj.style.width=sWidth + "px";
            bgObj.style.height=sHeight + "px";
            document.body.appendChild(bgObj);
            var msgObj=document.createElement("div")
            msgObj.setAttribute("id","msgDiv");
            msgObj.setAttribute("align","center");
            msgObj.style.position="absolute";
            msgObj.style.background="white";
            msgObj.style.font="12px/1.6em Verdana, Geneva, Arial, Helvetica, sans-serif";
            msgObj.style.border="1px solid " + bordercolor;
            msgObj.style.width=msgw + "px";
            msgObj.style.height=msgh + "px";
          msgObj.style.top=(document.documentElement.scrollTop + (sHeight-msgh)/2) + "px";
          msgObj.style.left=(sWidth-msgw)/2 + "px";
		  //msgObj.onmousedown=function beginDrag(this.parentNode,even);
          var title=document.createElement("div");
          title.setAttribute("id","msgTitle");
          title.setAttribute("align","left");
          title.style.margin="0";
          title.style.padding="3px";
          title.style.background=bordercolor;
          title.style.filter="progid:DXImageTransform.Microsoft.Alpha(startX=20, startY=20, finishX=100, finishY=100,style=1,opacity=75,finishOpacity=100);";
          title.style.opacity="0.75";
          title.style.border="1px solid " + bordercolor;
          title.style.height="18px";
          title.style.font="12px Verdana, Geneva, Arial, Helvetica, sans-serif";
          title.style.color="white";
			
			var dv1 = document.createElement("div");
				dv1.id="dv1";
				dv1.appendChild(document.createTextNode("会员登录"));
			title.appendChild(dv1);
			var dv2 = document.createElement("div");
				dv2.id="dv2";
				dv2.appendChild(document.createTextNode("关闭"));
			title.appendChild(dv2);	   	
		
          dv2.onclick=function(){
          document.body.removeChild(bgObj);
        document.getElementById("msgDiv").removeChild(title);
        document.body.removeChild(msgObj);
        }
          document.body.appendChild(msgObj);
          document.getElementById("msgDiv").appendChild(title);
		  
		  var pr2=document.createElement("p");
		  pr2.style.margin="0";
		  pr2.id="loginMessage";
		  document.getElementById("msgDiv").appendChild(pr2);
		  
		  var pr=document.createElement("p");
		  pr.style.margin="0";
		  pr.id="logintitle";
		 
	 	  document.getElementById("msgDiv").appendChild(pr);
		  
		  
		  document.getElementById("msgDiv").appendChild(document.createTextNode("用户名："));
		  
		  var input2=document.createElement("input");
		  input2.id="userName";
		  input2.type="text";
		  input2.style.width="120px";
		  document.getElementById("msgDiv").appendChild(input2);
		  
		  var br=document.createElement("br");
		  document.getElementById("msgDiv").appendChild(br);
		  
		  document.getElementById("msgDiv").appendChild(document.createTextNode("密  码："));
		  var input3=document.createElement("input");
		  input3.type="password";
		  input3.id="userPass";
		  input3.style.width="120px";
		  input3.className="des";
		  document.getElementById("msgDiv").appendChild(input3);
		  var br2=document.createElement("br");
		  document.getElementById("msgDiv").appendChild(br2);
		  
		  var checkBox2=document.createElement("input");
		  checkBox2.type="checkbox";
		  checkBox2.setAttribute("checked","true");
		  checkBox2.id="remember";
		  document.getElementById("msgDiv").appendChild(checkBox2);
		  var rem = document.createTextNode("记住我")
		 
		  document.getElementById("msgDiv").appendChild(rem);
		  var br3=document.createElement("br");
		  document.getElementById("msgDiv").appendChild(br3);
		  
		  var login=document.createElement("input");
		  login.type="button";
		  login.value="登录";
		  login.id="dl_login";
		  login.onclick=function(){checkLogin();}
		  document.getElementById("msgDiv").appendChild(login);
		  
		  var br4=document.createElement("br");
		  document.getElementById("msgDiv").appendChild(br4);	
		  
		  var span2=document.createElement("span");
		  var register=document.createElement("a");
		  register.href="/user/register.jsp";
		  register.target="_blank";
		  register.appendChild(document.createTextNode("注册"));
		  span2.appendChild(register);
		  var forget=document.createElement("a");
		  forget.href="/user/forget_password.jsp";
		  forget.target="_blank";
		  forget.appendChild(document.createTextNode("忘记密码"));
		  span2.appendChild(forget);
		  document.getElementById("msgDiv").appendChild(span2);	
	  //alert(document.getElementById("msgDiv").innerHTML);
      }

	var XMLHttpReq;
	function createXMLHttpRequest() {		
	    if (window.XMLHttpRequest) { //Mozilla 浏览器
	        XMLHttpReq = new XMLHttpRequest();
	    } else {
	        if (window.ActiveXObject) { // IE浏览器
	            try {
	                XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
	            }
	            catch (e) {
	                try {
	                    XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
	                }
	                catch (e) {
	                }
	            }
	        }
	    }
	}
	
	function checkLogin() {
		document.getElementById("loginMessage").innerHTML="";
		var userName=document.getElementById("userName").value;
		var userPass=document.getElementById("userPass").value;
		if(userName=="") {
			document.getElementById("loginMessage").innerHTML="<span style='color:red;'>用户名不能为空</span>";
			return false;
		}
		if(userPass=="") {
			document.getElementById("loginMessage").innerHTML="<span style='color:red;'>密码不能为空</span>";
			return false;
		}
		if(!(userName<='z'&&userName>='a')) {
			document.getElementById("loginMessage").innerHTML="<span style='color:red;'>用户名只能为字母</span>";
			return false;
		}
		if(userName.length<4) {
			document.getElementById("loginMessage").innerHTML="<span style='color:red;'>用户名必须大于三位</span>";
			return false;
		}
		if(userName.length>20) {
			document.getElementById("loginMessage").innerHTML="<span style='color:red;'>用户名不能大于20位</span>";
			return false;
		}
		var remember="0";
		if(document.getElementById("remember").checked==true) {
			remember="1";
		}
		var url="task=user&step=login&userName="+userName+"&userPass="+userPass+"&remember="+remember;
		createXMLHttpRequest();
		XMLHttpReq.open("POST","/loginAjax.do", true);
     	XMLHttpReq.onreadystatechange = processUserLoginResponse;	//指定响应函数
    	XMLHttpReq.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");   //这句话是确保服务器知道请求体中有请求参数  
    	XMLHttpReq.send(url);		
	}
	
	function processUserLoginResponse() {
    	if (XMLHttpReq.readyState == 4) { // 判断对象状态
        	if (XMLHttpReq.status == 200) { // 信息已经成功返回，开始处理信息
				var xmlDoc =XMLHttpReq.responseXML;
				var flag=xmlDoc.getElementsByTagName("flag")[0].firstChild.data;
				var userName=xmlDoc.getElementsByTagName("userName")[0].firstChild.data;
				var userPass=xmlDoc.getElementsByTagName("userPass")[0].firstChild.data;
				var remember=xmlDoc.getElementsByTagName("remember")[0].firstChild.data;
				var userId=xmlDoc.getElementsByTagName("userId")[0].firstChild.data;
				if(flag==1) {
					document.getElementById("loginMessage").innerHTML="<span style='color:red;'>用户名不存在</span>";
				}else if(flag==2) {
					document.getElementById("loginMessage").innerHTML="<span style='color:red;'>密码错误</span>";
				}else if(flag==3) {
					document.body.removeChild(document.getElementById("bgDiv"));
					document.getElementById("msgDiv").removeChild(document.getElementById("msgTitle"));
					document.body.removeChild(document.getElementById("msgDiv"));
					if(remember==1) {
						setCookie("peyedUserName",userName,"7300",null,null,null);
						setCookie("peyedUserPass",userPass,"7300",null,null,null);						
					}
					document.getElementById("puserNameId").value=userId;
  					sendUserIsLoginRequest('/userAjax.do?task=user&step=isLogin');					
				}
            } else { //页面不正常
                window.alert("您所请求的页面有异常");
            }
        }		
	}	


function setCookie(name,value,expires,path,domain,secure){
	//alert(value);
	var expDays = expires*24*60*60*1000;
	var expDate = new Date();
	expDate.setTime(expDate.getTime()+expDays);
	//alert("path="+path);
	var pathString = ((path==null) ? "/" : (";path="+path))
	var expString = ((expires==null)?"/":(";expires="+expDate.toGMTString()));
	var domainString = ((domain==null) ? "" : (";domain="+domain))
	var secureString = ((secure==true) ? ";secure": "" )
	document.cookie = name + "=" + escape(value) + expString + pathString + domainString + secureString;
} 

//获取指定名称的cookie值：
function getCookie(name){
	var result = null;
	var myCookie = document.cookie + ";";
	var searchName = name + "=";
	var startOfCookie = myCookie.indexOf(searchName);
	var endOfCookie;
	if (startOfCookie != -1){
		startOfCookie += searchName.length;
		endOfCookie = myCookie.indexOf(";",startOfCookie);
		result = unescape(myCookie.substring(startOfCookie, endOfCookie));
	}
	return result;
} 

//删除指定名称的cookie：
function clearCookie(name){
	var ThreeDays=3*24*60*60*1000;
	var expDate = new Date();
	expDate.setTime(expDate.getTime()-ThreeDays);
	document.cookie=name+"=;expires="+expDate.toGMTString();
} 		

	function getFormAsString(formName,startStr){	
	 	var query_string =startStr;
	 	var and='&';
	 	form_obj=document.forms[formName].elements;
	    for (var i=0;i<form_obj.length ;i++ )
	    {
	        e=form_obj[i]; 
	        if (e.name) {
	            if (e.type=='select-one') {
	                element_value=e.options[e.selectedIndex].value;
	            } else if (e.type=='select-multiple') {
	                for (var n=0;n<e.length;n++) {
	                    var op=e.options[n];
	                    if (op.selected) {
	                        query_string+=and+e.name+'='+encodeURIComponent(op.value);
	                        and="&"
	                    }
	                }
	                continue;
	            } else if (e.type=='checkbox' || e.type=='radio') {
	                if (e.checked==false) {   
	                    continue;   
	                }   
	                element_value=e.value;
	            } else if (typeof e.value != 'undefined') {
	                element_value=e.value;
	            } else {
	                continue;
	            }
	            query_string+=and+e.name+'='+encodeURIComponent(element_value);
	            and="&"
	        }
	
	    }
	    return query_string;
	 }