Personally I'm never bothered so much by the user interface as long as the site content is presented in a nice and simple way that is readable by everyone. So far I think you are doing fine in the...

How about adding a die statement to assist in debugging like so

$this->con=mysql_connect($server,$name,$pass) or die(mysql_error());


happy times!

What you need is simply DHTML. Just like Gmail's attach another file, you need something like that which when clicked will add two text fields for item code and another one for serial no.
So the...

<?php

$row_count = 0;
$columns = 3;

while ($row = mysql_fetch_assoc($result)) {

if ($row_count == $columns) {

echo "</tr><tr>";