function IsNull(str)
{
	return (str.replace(/^\s+|\s+$/g,"")=="");
}

function check()
{
  var form=document.forms["userinfo"];
	if(IsNull(form.username.value))
  {
    form.username.focus();
    alert("User Name Not is null, please input!");
    return false;
  }
  if(IsNull(form.Firest_Name.value))
  {
    form.Firest_Name.focus();
    alert("Your Firest_Name Not is null, please input!");
    return false;
  }
  if(IsNull(form.Last_Name.value))
  {
    form.Last_Name.focus();
    alert("Your last Name Not is null, please input!");
    return false;
  }
  if(form.username.value.length<3)
  {
    form.username.focus();
    alert("User Name Length must >3,please input!");
    return false;
  }
  if(IsNull(form.password.value)||form.password.value.length<6)
  {
    form.password.focus();
    alert("Password Length must >6,please input!");
    return false;
  }
  if(form.password.value!=form.re_pass.value)
  {
    form.password.focus();
    form.password.value='';
    form.re_pass.value='';
    alert("Two different input password, please re-entry. ");
    return false;
  }
  var email=form.username;
  if(email.value.length!=0)
  {
    if(email.value.charAt(0)=="."||email.value.charAt(0)=="@"||email.value.indexOf('@',0)==-1||email.value.indexOf('.',0)==-1||email.value.lastIndexOf("@")==email.value.length-1||email.value.lastIndexOf(".")==email.value.length-1)
    {
      alert("Email address format is not correct! ");
      email.focus();
      return false;
    }
  }
  else
  {
    alert("Email not empty! ");
    email.focus();
    return false;
  }
}