I am using the Facebook comments plugin on a blog I am building. It has some FBXML tags that are interpreted by the facebook javascript that is referenced on the page.

This all works fine, but I have to pass in the current, fully-qualified URL to the plugin.

<div style="width: 900px; margin: auto;">
    <div id="fb-root"></div>
    <fb:comments href="URL HERE" num_posts="10" width="900"></fb:comments>
</div>