ช่วยดู code ทีครับ หน้าล๊อคอิน บางทีมันไม่ยอมเช็ค user ก่อนใส่รหัสมั่วก็เข้าได้อ่ะครับ

<?
	session_start();
	session_register("username");
	session_register("name");
	session_register("type");
	session_register("company_name");
	mysql_connect("localhost","root","5555");
	mysql_select_db("sta444");
	$strSQL = "SELECT * FROM tb_stluser WHERE username = '".trim($_POST['username'])."' 
	and password = '".trim($_POST['password'])."'";
	$objQuery = mysql_query($strSQL);
	$objResult = mysql_fetch_array($objQuery);
	if(!$objResult)
	{
			//echo 'wrong';
			$code_error = "ข้อมูลไม่ถูกต้อง Login ใหม่ !!";
			session_register("code_error");
            //print "<meta http-equiv=refresh content=0;URL=index.php?//>";
			header("location:index.php");
	}
	else
	{
			$_SESSION["username"] = $objResult["username"];
			$_SESSION["name"] = $objResult["name"];
			$_SESSION["type"] = $objResult["type"];
			$_SESSION["company_name"] = $objResult["company_name"];

			session_write_close();
			
			if($check == "on")
			{
				setcookie("username",$username,time()+3600*24*356);
				setcookie("password",$password,time()+3600*24*356);
				if($objResult["type"] == "Dealer")
				{
					header("location:stl_dealer.php");
				}
				else
				{
					header("location:stl_admin.php");
				}
			}else {
				if($objResult["type"] == "Dealer")
				{
					header("location:stl_dealer.php");
				}
				else
				{
					header("location:stl_admin.php");
				}
			}
	}
	mysql_close();
?>

<? 
session_start();
if (!$_SESSION["username"]) {
			echo '
<?php
	 session_start();
	 session_unregister("username");
	 session_unregister("name");
	 session_unregister("type");
	 session_unregister("company_name");
	 session_unregister("code_error");
?>
<script language="javascript">
function check()
{
	if(document.getElementById("username").value.length == 0)
	{
		alert("คุณยังไม่ได้กรอก User Name ครับ");
	}
		else if(document.getElementById("password").value.length == 0)
		{
			alert("คุณยังไม่ได้กรอก Password ครับ");
		}
}
</script>
<td height="205" background="images/head_login.jpg" valign="top" style="background-repeat:no-repeat; padding-top:10px; padding-left:10
px; text-align: center; color: #090;"><form id="form1" name="form1" method="post" action="checkuser.php">
     <p>&nbsp;</p>
     <table width="260" border="0" align="center">
       <tr>
         <td width="80" class="darkgray13"><div align="left">User Name</div></td>
         <td width="110"><label for="textfield"></label>
           <div align="left"><input name="username" type="text" id="textfield" size="15" maxlength="10" /></div></td>
       </tr>
       <tr>
         <td class="darkgray13"><div align="left">Password</div></td>
         <td><label for="textfield2"></label>
           <div align="left"><input name="password" type="password" id="textfield2" size="15" maxlength="10" /></div></td>
       </tr>
       <tr>
         <td class="darkgray13"><div align="left">Remember Me?</div></td>
         <td><div align="left"><input type="checkbox" name="checkbox" id="checkbox" value="on" /></div></td>
       </tr>
       <tr>
         <td colspan="2"><div align="center">
           <input type="submit" name="submit" id="submit" value="เข้าสู่ระบบ" onClick="check();">
         </div></td>
         </tr>
   </table>
	<id class="red"><div align="center">'.$code_error.'</div></id>
   </form>
   </td>
			';
}else{
		session_unregister("code_error");
		echo '
		<td height="205" background="images/head_login.jpg" valign="top" style="background-repeat:no-repeat; padding-top:10px; padding-left:10
px; text-align: center; color: #090;"><form id="form1" name="form1" method="post" action="">
     <p>&nbsp;</p>
			<div class="whitelink">
				<strong><id class="darkgray13">ยินดีต้อนรับคุณ '.$_SESSION["name"].' </id><br /><id class="darkgray13">บริษัท '.$_SESSION["company_name"].'</id><br />
				 <a href="stl_admin.php">เข้าสู่ระบบ</a>&nbsp;&nbsp;  <a href="index.php">แก้ไขข้อมูล</a> &nbsp;&nbsp;  <a href="stl_logout.php">ออกจากระบบ</a></strong><br /><br />
			</div>
			</td>
	';
}
?>