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.
Past visits are categorized into four â€œbuckets,â€ based on the days since the visit. The visits in each bucket are given a different weight for frecency calculations. These preferencesâ€”of the form places.frecency.*BucketCutoffâ€”determine the various cutoffs, in days, for the four possible buckets.
Possible values and their effects
The number of days since the visit required for a visit to fall into a given â€œbucket.â€
By default, the following preferences and values exist, defining four buckets:
First checked in
Has an effect in