From MozillaZine Knowledge Base
Firefox 2.0 introduces in-browser feed handling. In the feed preview interface, users can choose to subscribe to the feed using an application or web site. This preference, along with browser.contentHandlers.types.*.type and browser.contentHandlers.types.*.uri, determines which web sites are listed in the â€œSubscription Optionsâ€ dialog.
This is an enumerated preference: all preferences whose names start with browser.contentHandlers.types. are read to generate the list of web sites. The * in the preference name is a non-negative integer, and matches the number in the two other preferences needed to describe a feed-handling web site. (For example: browser.contentHandlers.types.0.title, browser.contentHandlers.types.0.type, and browser.contentHandlers.types.0.uri describe one website to be listed in the dialog.) It also determines the order in which the web sites appear in the dialog.
Preferences of this form were briefly named browser.contentHandlers.types.title* before this name was decided.
Possible values and their effects
By default, the following preferences and values exist:
First checked in
Has an effect in