Hmmm, maybe I wasn't clear on this subject. I'm looking for something like that:
<?php
if (isset($_COOKIE['ubb_style']) && ($_COOKIE['ubbstyle'] == 'mystyle'))
{
echo '<a href="<img src="images/header_mystyle.gif">';
}
else
{
echo '<a href="<img src="images/header_otherstyle.gif">';
}
?>
Actually, now I will just look for cookie/session name and the problem will be solved.

Thanks.