Part of UI improvements Mozilla removed “Recent Pages” drop down button from Firefox 4, in Firefox 3.x versions this arrow shows recent history of visited pages in a drop down menu next to navigation arrows which allows user to go back to previously visited pages.
Most convenient and useful feature removed just for the sake of Browser-envy. Now Firefox 4 & 5 users have to right-click on the forward button to get recent history drop down. As we know extensions restore features to Firefox (reminding about useful Status-4-Evar extension in case of Firefox 4 status bar) Back/Forward dropmarker Firefox add-on adds a drop marker to combined back/forward button.
This add-on is works with Firefox 4 – 8.0 a1. Another add-on Backward Forward History DropDown does the same also.