Comment out the following lines in index.php, so that it looks like this:
[PHP]<!– BEGIN: MAIN NAVIGATION
<div id=”ja-mainnavwrap1″>
<div id=”ja-mainnavwrap2″>
<div id=”ja-mainnav” class=”clearfix”>
<?php
echo $topnav;
?>
</div>
</div>
</div>
END: MAIN NAVIGATION –>
[/PHP]
The background of the menu items is integrated into the menu images – so you have to modify these images in /images: top_nav_left.gif, top_nav_right.gif, topnav_n_left.gif, topnav_n_right.gif and top_nav_bg3.gif; and for a perfect styling as well the images topnav_wrap_bg.gif – topnav_wrap_bg3.gif.