The easiest way if you need to:
1) Click a button which defines select option
2) Go to another page, where select option is
3) Have that option value selected on another page
1) your button links (say, on home page)
<a onclick="location.href='contact.php?option=1';" style="cursor:pointer;">Sales</a>
<a onclick="location.href='contact.php?option=2';" style="cursor:pointer;">IT</a>
(where contact.php is your page with select options. Note the page url has ?option=1 or 2)
2) put this code on your second page (my case contact.php)
<?
if (isset($_GET['option']) && $_GET['option'] != "") {
$pg = $_GET['option'];
} ?>
3) make the option value selected, depending on the button clicked
<select>
<option value="Sales" <? if ($pg == '1') { echo "selected"; } ?> >Sales</option>
<option value="IT" <? if ($pg == '2') { echo "selected"; } ?> >IT</option>
</select>
.. and so on.
So this is an easy way of passing the value to another page (with select option list) through GET in url. No forms, no IDs.. just 3 steps and it works perfect.