F6 focuses the first selectable element in the user interface. If "Tabs on Top" is selected then the active tab is selectable, so the location bar is not selected. First press F6 and then press the Tab key to set focus to the location bar. You may need to press the Tab key several times if there are other elements that can have focus.

To get the 3.6 behavior uncheck "Firefox > Options > [ ] Tabs on Top" or use Ctrl + L or Alt + D to access the location bar.

You can look at this extension:

• F6: https://addons.mozilla.org/firefox/addon/f6/

The F6 shortcut to the Address Bar is standard functionality in all browsers and has been since the beginning of time. With the release of V.4 this has been changed, in Firefox alone and I see that V.5 has the same. I rely very heavily on keyboard shortcuts to work efficiently and speedily and this is a really big let down from my favorite browser. Please restore the feature. I've had to look at alternative browsers that do support this feature.