It takes simple text with font modifiers like
<b>...</b>. This can be used for example to put a copyright notice at the bottom of the page It isn't clear how sophisticated the html can get.
If you want to have more text and things like external counters in your footer, put this in your config-file:
$FooterNote = "<iframe src=./footer.html type=text/html width=100% height=90 frameborder=0 scrolling=no></iframe>"; # HTML for bottom of every page
Create a file named footer.html with your html-code. --BernhardZechmann