Live Bookmarks is a new technology in Firefox that lets you view RSS news and blog headlines in the bookmarks toolbar or bookmarks menu. With one glance, quickly see the latest headlines from your favorite sites. Go directly to the articles that interest you — saving you time.
See picture below:
As picture tells there is a little RSS button on page when there is a rss feed available for page contents. When you click it Firefox creates new folder into bookmarks with feed links and titles.
More information in Mozilla.org