Yesterday's post about Yahoo's attempt to win Firefox search share back from Google contained two screen shots. Looked fine on the website, but the images were broken when Feedburner syndicated that content as RSS feeds and the email version. (Sorry about that!)
The reason? Relative links.
Relative links (eg '/content/yahoo2.JPG') work fine for folks reading the blog on the site, but fail off-site. The email client or the RSS reader doesn't know the base for these links. Absolute links (eg '/sites/default/files/content/yahoo2.JPG') will always work.
Two take-aways here: first, realize that much of your RSS content will be read off-site, and so you need to ensure it looks right in whatever channel it ends up. Second: stick with absolute URLs in your feeds, absolutely.