// JavaScript Document
function user_isok(theform)
{
if (theform.username.value=="")
  {
    alert("用户名不能为空");
    theform.username.focus();
    return (false);
  }
if (theform.Password.value=="")
  {
    alert("密码不能为空");
    theform.Password.focus();
    return (false);
  }
if (theform.check_code.value=="")
  {
    alert("验证码不能为空");
    theform.check_code.focus();
    return (false);
  }
return (true);
}