In the click handler for loading ajax pages, you can replace the comment code in facebook with the code for new pages
<fb:comments href="example.com" num_posts="2" width="500"></fb:comments>
Replace example.com with the URL of the page. Also, this refers to the header:
<script src="http://connect.facebook.net/en_US/all.js#appId=188677664483920&xfbml=1"></script>
: API facebook xfbml , FB.XFBML.parse();
, , .