Zkus toto:

# Open and launch FireFox 2.
# Go to FireFox preferences editing page by keying in “about:config” (without quotes) in the FireFox’s address bar at Navigation Toolbar, then press Enter or click on the green Go.
# Typing the name of the preference in the filter box. In this case, the preference that need to be changed is browser.tabs.closeButtons. You can also scroll down and browse the list of options to locate it.
# Double click on browser.tabs.closeButtons, or right click on it and then select Modify.
# At the “Enter integer value” window, enter one of the following values to change the position and location of tabs’ close button to the value that suit your preference:

0: One close button only on the active tab.
1: Each tabs has its own close button (default)
2: Removes all close buttons (no close button, right click to select option to close the tab).
3: Display a single close button at the end of the tab strip bar (style as in Firefox 1.5).

Press OK when done.