Looking at your source code reveals that this is being rendered above your HTML declaration:
$txt['topic_starter'] = 'Topic starter';
// Avatars at Index Mod By alperuzi
$txt['enable_mini_avatars'] = 'Enable displaying mini avatars at message index';
$txt['enable_memberlist_avatars'] = 'Enable displaying avatars at member list <div class="smalltext">Avatars on the member list appear full size.</div>';
$txt['miniAvatarHeight'] = 'Avatar height (pixels) <div class="smalltext">To scale by width only, enter 0.</div>';
$txt['miniAvatarWidth'] = 'Avatar width (pixels) <div class="smalltext">To scale by height only, enter 0.<br>For full size avatars enter 0 to both fields.</div>';
$txt['avatar'] = 'Avatar';
// End Of Avatars at Index Mod
Can you attach your index.template.php for that theme or look at that file and see if it's in there as well?