From MozillaZine Knowledge Base
In Firefox 3, the Location Bar received a number of improvements. Among those improvements was the move to a XUL richlistbox widget for the auto-complete dropdown. This allowed styled URL/title information, favicons, and highlighted match information. Typing in the Location Bar will now search not only URLs, but page titles, bookmark names, and tags.
Due to the amount of information available when searching those sources, it’s easy to come across cases where typed text will match useless items (e.g., typing “ebay” might bring up a match for “thepiratebay”). To address this, word boundaries are taken into account when searching for matches, making text that matches against the start of a word rank higher than text matching inside a word (e.g., “eb” matching “ebay” over “website”).
This preference determined whether or not to use word boundaries when searching for items in the Location Bar. It has since been obsoleted by browser.urlbar.matchBehavior.
Possible values and their effects
Use word boundaries when searching for typed text in the Location Bar autocomplete. (Default)
Search anywhere within available text, irrespective of word boundaries.
First checked in
Has an effect in