Well, that's what size your buttons are...
They are loaded as a background for h3 in your right column with this bit of CSS -
#right H3, h2.widgettitle
background: url(images/title.gif) repeat-x/**not sure why that would be repeated**/
You also have a class on that h3 that your not styling in CSS-
<div class="menu"> <h3 class="menu-header">Pages</h3> <ul>
<li class="page_item page-item-7">