Try the Firefox Safe Mode to see how it works there. The Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• You can open the Firefox 4.0+ Safe Mode by holding the Shift key when you use the Firefox desktop or Start menu shortcut.
• Or use the Help menu item and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Don't select anything right now, just use "'Start in Safe Mode" To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before using the Firefox shortcut (without the Shift key) to open it again. If it is good in the Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one.

Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

That means that you have more than one copy of a bookmark in different folders.
That usually only happens if you made such a copy yourself because otherwise you only update the current bookmark if you click the yellow highlighted star on the location bar.

You can check that via the search bar in the Bookmarks and History Manager (Library) or Bookmarks sidebar (Ctrl+B)

• Bookmarks > Show All Bookmarks
• View > Sidebar > Bookmarks

Press the F10 key or tap the Alt key to bring up the "Menu Bar" temporarily if the menu bar is hidden.