To validate against the [URL=http://www.cynthiasays.com/]Cynthia Says section 508 validator[/URL], the RSS feed widget needs alt text:

inc/widgets/widgets/_coll_xml_feeds.widget.php
line 114

-$title = str_replace( '$icon$', '<img src="'.$rsc_url.'icons/feed-icon-16x16.gif" width="16" height="16" class="top" alt="" /> ', $this->disp_params['title']);
+$title = str_replace( '$icon$', '<img src="'.$rsc_url.'icons/feed-icon-16x16.gif" width="16" height="16" class="top" alt="RSS icon" /> ', $this->disp_params['title']);