Sjoerd: While reading your linked post, I noticed this: "Finally I'd like to share a trick to set the base URI for escaped HTML in RSS and Atom: add a BASE element to the beginning of the HTML content."
Maybe I shouldn't be, but I'd be surprised if that worked in too many aggregators. After all the warnings (and platypus attacks) over the years, I know that I strip pretty much any non-essential markup/attributes from incoming RSS/Atom items, including html:base. -- Roger Benningfield
