Google Toolbar for Firefox is compatible with Firefox version 4 or older. To find out what version of Firefox you’re using, click the Help menu and select “About Firefox” (on the Mac, the option is located in the “Firefox” menu).

If you use Firefox version 5 or newer, you won’t be able to use Google Toolbar. However, you can still add similar functionality to the browser by trying one or more of the following Firefox add-ons:

• AutoFill: See available add-ons to fill out forms.
• Page translation: See available translation add-ons.
• Find in page: Use the built-in feature in Firefox by pressing Ctrl-F (in Windows and Linux) or Command-F (on Mac).
• Spell-check: Use built-in spell-check in Firefox.
• Page sharing: Consider using other add-ons for sharing.
• Site thumbnails on a new tab: Try out some of the other add-ons for generating site thumbnails.
• Bookmarks: See available bookmark add-ons. To access your Google Bookmarks visitwww.google.com/bookmarks.
• Gmail notifications: See available Gmail add-ons.

The above list is provided only for your convenience. Google does not make any warranties or guarantees about any add-ons. Always be careful when installing add-ons as they may cause security, performance, or instability issues.

Read more at http://support.google.com