what do you mean? firefox4 support 2 layout style, one is firefox 4.0 new style, much more similar to google chrome, another is traditional firefox, similar to firefox 3.x, well, how to do this, 1st. install firefox 4.o from mozilla official, 2nd, see firefox main window, the firefox button most left-top there? click it! then options, don't click, hang your mouse cursor on the "options", then you'd see a small sub menu, for tabs, navigation pane, bookmark bar, enable/disable the page-tabs to the top-most, and traditional menus, so tick those you want, and if you are in traditional style, right-click the menu bar there(i.e. right-click help menu button), you will see a small menu for you to customize the firefox upper parts, you can tick things you want or not, i.e. disable menu bar, to make firefox 4 going in the new style.