From MozillaZine Knowledge Base
Firefox 3 introduced a number of improvements to the Location Bar. Among them were changes to how sites are ordered in the dropdown menu. Firefox takes into account how frequently and how recently sites in the browser history were visited, combining them into a statistic called â€œfrecency.â€ The frecency of sites is calculated when the browser is idle. The way frecency is computed can be tweaked by a number of preferences.
When a given place has had no visits (perhaps as a result of clearing private data) the frecency must be estimated. These preferencesâ€”of the form places.frecency.unvisitedBookmarkBonus and places.frecency.unvisitedTypedBonusâ€”determine the bonus given to these two kinds of URLs when estimating the frecency.
Possible values and their effects
The percent bonus given to unvisited URLs.
By default, the following preferences and values exist:
First checked in
Has an effect in