Please note that this special category is intended for sidebar tabs for browsers derived from Mozilla only, and thus is not suitable for browsers such as Internet Explorer, Opera or Safari. For usual sites, you will have to look for the right category. Keep in mind that submitting a site in a wrong category would considerably delay its review.
You have probably noticed that links listed here are of the following form:
This category lists sidebars tabs for browsers based on Mozilla, i.e. Firefox, the all in one SeaMonkey suite, Flock and others.
These tabs are used to display shortcuts, useful links, short summaries or news feeds from a given site on a sidebar that users can open whenever they want.