function checkdata()
{ 
var user=document.getElementById("username")
var uEmpt=document.getElementById("userEmpt")
if(user){
if(user.value==""){
userEmpt.innerHTML='用户名不能为空'
user.focus();
return false;
}
else{
uEmpt.innerHTML=''
}
}
var pwd=document.getElementById("pwd")
var pwdEmpt=document.getElementById("pwdEmpt")
if(pwd){
if(pwd.value==""){
pwdEmpt.innerHTML='密码不能为空'
pwd.focus();
return false;
}
else{
pwdEmpt.innerHTML=''
}
}

var myreview=document.getElementById("myreview")
var reviewEmpt=document.getElementById("reviewEmpt")
if(myreview.value==""){
reviewEmpt.innerHTML="请填写评论"
myreview.focus();
return false;
}
else{
reviewEmpt.innerHTML=""
}
return true;
}