ต้องการเช็คค่างว่างและinsert ลง database (ทำไม ie insert 2 รอบ Firefox รอบเดียว)

/* javascript */

function chknull()
	{
		if(document.frmAddCatagory.typename.value==""||document.frmAddCatagory.typename.value==null)
		{
			alert('Please insert typename !');
			document.frmAddCatagory.typename.focus();
			return false;
		}
		if(document.frmAddCatagory.typedetail.value==""||document.frmAddCatagory.typedetail.value==null)
		{
			alert('Please insert typedetail !');
			document.frmAddCatagory.typedetail.focus();
			return false;
		}
		
		return true;
		/*document.frmAddCatagory.submit();*/
		
	}



/*----------------------------------------------------------------------------------*/

/* form */

<form id="frmAddCatagory" name="frmAddCatagory" method="POST" action="insert_catagory.php" onsubmit="return chknull();">
						<table width="100%" cellspacing="0" cellpadding="1" bordercolor="#ffffff" border="1" class="textform">
        				<tbody>
							<tr bgcolor="#7db00d"> <td height="30" colspan="3">
            					<table width="100%" height="20" cellspacing="0" cellpadding="0" border="0">
                				<tbody>
								<tr>
                    				<td width="25%" align="left">
                        				<span class="subheadnews">
											เพิ่มหมวด
										</span>                        	
									</td>
                            		<td align="right" width="75%">&nbsp;</td>
                        		</tr>
                    			</tbody>
								</table>
				   
                			</td>
            			 </tr>
						 <tr> 
                      		<td height="25" width="25%" bgcolor="#e5e5e5" align="right">
								<span class="subhead">
									ชื่อหมวด&nbsp;:&nbsp;
								</span>&nbsp;
							</td>
                      		<td height="25" bgcolor="#e5e5e5" colspan="2" align="left">
								&nbsp;&nbsp;&nbsp;&nbsp;<input type="text" name="typename" id="typename" />
							</td>
                    	</tr>
                    	<tr> 
                      		<td class="subhead_over" width="25%" height="50" align="right" valign="top" bgcolor="#fffafa">
								<span class="subhead">
									รายละเอียด&nbsp;:
								</span>&nbsp;&nbsp;
							</td>
                     		<td height="220" bgcolor="#e5e5e5" colspan="2" align="left">
								&nbsp;&nbsp;&nbsp;&nbsp;<textarea class="textform" name="typedetail" id="typedetail"  style="
								background-color: rgb(255, 255, 238); font-family: MS Sans Serif; font-size: 10pt; border-style: solid; 
								border-width: 1px;" cols="54" rows="12" ></textarea>
							</td>
                    	</tr>
                    					
					
                    	<tr bgcolor="#e5e5e5"> 
                      	<td height="30" colspan="3" align="center" bgcolor="#e5e5e5">
							<span class="subhead">
								&nbsp;
					  		<font color="#ff0000"><input type="submit" name="btnSubmit" value="บันทึก" />
							</font>
							</span>
					  	</td>
                    </tr>
          			</tbody>
					</table>
						</form>


/*----------------------------------------------------------------------------------------------*/

/*  insert_catagory.php  */

<?
	$typename = $_POST['typename'];
	$typedetail = $_POST['typedetail'];
	
	//echo $typename."<br />".$typedetail;    มีค่า
	
	
	include "connect.php";
	include "function.php";
	
	$today = date("Y-m-d H:i:s"); 
	
	$sql1 = "INSERT INTO kmtype (typename,typedetail,groupid,typedate,typeflag)
			 VALUES ('$typename','$typedetail','1','$today','0')";
		
	$result1 = mysql_db_query($dbname,$sql1);
	
	if($result1)
	{
	//	echo "บันทึกเรียบร้อยแล้ว";
		echo "<script language='JavaScript'>"; 
		echo "alert('บันทึกเรียบร้อยแล้ว');"; //ถ้า alertตอนนี้มันจะ error head ครับ
	//	echo "window.close();";
		echo "window.location='manage_catagory.php'";
	//	echo "window.opener.location.reload();";
	//	echo "<meta http-equiv='refresh' content='0;URL=manage_catagory.php?'>";
		echo "</script>"; 
		
	}
	else
	{
	//	echo "บันทึกไม่ได้";
		echo "<script language='JavaScript'>"; 
		echo "alert('บันทึกไม่ได้');"; //ถ้า alertตอนนี้มันจะ error head ครับ
	//	echo "window.close();";
		echo "window.location='add_catagory.php'";
	//	echo "window.opener.location.reload();";
	//	echo "<meta http-equiv='refresh' content='0;URL=manage_catagory.php?'>";
		echo "</script>"; 
	}	
		
mysql_close($link);

?>