styling a select box, using php, ..not working...need help

Hi all.
I am really hoping that someone can point me in the right direction with my problem.

I am doing a site that uses css and php.

I am trying to use a select box that gets its contents from the database.

when I made the page layout in css I styled the select box in the webpage as so:
<div id="tmphldr"><select name="select" class="x">
<option>Product Type</option>
<option>Product Type2</option>
</select>
</div>

a div that holds the select box + the select box

in the css file I wrote this:

#tmphldr
{
float: left;
width: 160px;
height: 22px;
line-height: 22px;
border: 1px solid White;
background-color: #FFBFDC;
margin-top: 2px;
margin-left:15px;
margin-right: 5px;
text-align: center;
color: #ba2742;
}

and


.x {
width: 160px;
height: 18px;
margin-top: 1px;

border: 1px solid #ba2742;
font-size: 12px;
color: #ba2742;
}


now using these values gave me what I wanted with both mozilla and IE.

then I (my partner) added the php code to the webpage and the code for the select box looks like this now:
<div id="tmphldr">
<form method="post">
<input type="hidden" value="l" name="type" />
<?=DBDropDownListOnChange("select pk_id, line_name from line order by line_name", "line_name", "pk_id", "id", $line_id, "product.php","-- LINE Names --", "x")?>
</form>
</div>


Now the select box works fine, the data comes in as required, but in IE the surrounding div <div id="tmphldr"> has now expanded downwards, roughly doubling its size.

I cant figure how to make it look as it was supposed to.


Can anyone offer any advice?

Thanks

Sami