From MozillaZine Knowledge Base
When the default for layout.word_select.stop_at_punctuation was changed for Firefox Unix builds in bug 190615, a side effect was that selecting the entire URL in the Location Bar required triple-clicking. To restore the original double-click-selects-all behavior, this preference (and corresponding Location Bar code) was added to Firefox. It is not present in SeaMonkey 2.0.x (bug 611162).
Possible values and their effects
Select the contents of the Location Bar when double-clicking anywhere inside it. (Default in Unix [but not OS X])
Select the word under the cursor in the Location Bar when double-clicking inside it. (Default elsewhere)
First checked in
2007-08-04 by Wolfgang Rosenauer (patch by DÃ£o Gottwald)
Has an effect in