Here is the code to get rid of the compatiblity mode error. This code also sets one comment box per cms article, so you dont have all the comments mixed in alle the articles.
Code:
<!-- FB Comments -->
<h2 class="blockhead" style="padding-top:5px;"><span class="optiontitle">Facebook Kommentare</span></h2>
<div id="thread_tags_list" class="thread_info_block blockbody formcontrols floatcontainer">
<div class="blockrow floatcontainer">
<div id='tag_list_cell'>
<div id="fb-root"></div><script src="http://connect.facebook.net/en_US/all.js#appId=YOURAPPID&xfbml=1"></script><fb:comments href="http://www.YOURSITE.com/{vb:raw relpath}" expr:xid="YOUR-APP-ID" simple="1" num_posts="10" width="500" publish_feed="true"></fb:comments><br/>
</div>
</div>
</div>
<img src="clear.gif" height="10" /><br />
<!-- /FB Comments -->
just change all the stuff, just a little sidenote, the link in href isnt vbseo compatbile. i dont think that should be a big problem.