Try this:

Tape about:config in the address bar then enter Accept the warning Search browser.uiCustomization.state Right-click on the value, something like {"placements":{"PanelUI-contents… Click on Reset Close and open again Firefox and check if your problem is solved

Sorry, no luck.  :(

You can check for problems with the places.sqlite database (bookmarks and history) in the Firefox profile folder.

• https://addons.mozilla.org/firefox/addon/places-maintenance/

See also:

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

Make sure that toolbars like the "Bookmarks Toolbar" are visible.

• "3-bar" menu button > Customize > Show/Hide Toolbars
• View > Toolbars
  You can tap the Alt key or press F10 to show the Menu Bar
• Right-click empty toolbar area

Open the Customize window and set which toolbar items to display.

• "3-bar" menu button > Customize

• check that "Bookmarks Toolbar Items" is on the Bookmarks Toolbar
• if "Bookmarks Toolbar Items" is not on the Bookmarks Toolbar then drag it back from the Customize palette to the Customize window to the Bookmarks Toolbar

• if missing items are in the Customize palette then drag them back from the Customize window to the toolbar
• if you do not see an item on a toolbar and in the Customize palette then click the Restore Defaults button in the Customize palette window to restore the default toolbar set.

• https://support.mozilla.org/kb/customize-firefox-controls-buttons-and-toolbars
• https://support.mozilla.org/kb/navigation-buttons-missing

SInce Cor-el's advice I discovered that the customise options were not appearing when the option was selected. The window opened but it was just blank.

So I decided to "refresh firefox" via the Help>Troubleshooting Information option. This removed all addons and everything worked fine until Sync very kindly put all my addons back on and the faults re-occured. So I set Sync not to sync addons and refreshed again.

For some unknown reason Sync put Plugins back on but not extensions. So with no extensions running everything has been working fine. One of the extensions must have been causing the problem.

It would be handy to have an option to turn off plugins and extensions seperately for fault finding purposes.

Thanks for everyones input and help.

Plugins are always installed because Firefox finds them via a scan of the Windows Registry and plugins aren't installed in the Firefox profile folder like extensions are.

• https://developer.mozilla.org/Add-ons/Plugins/Gecko_Plugin_API_Reference/Plug-in_Basics#How_Gecko_Finds_Plug-ins