go to help at the top of your browser then click on restart with add-ons disabled, firefox will close then it will open up with just basic firefox, then you can swicth the add-ons back on and it should be ok, ive just done this myself and it worked

i did this after i restarted + add ons disabled it gave me a list of setting with tick boxes then i got stuck i pressed continue in safe mode. i opened up your reply and the screen is shifted to right still im confused!!

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

If it does work in Safe-mode then disable all extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

• Use "Disable all add-ons" on the Safe mode start window to disable all extensions.
• Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

In Firefox 4+ you can use one of these to start in Safe mode:

• Help > Restart with Add-ons Disabled
• Hold down the Shift key while double clicking the Firefox desktop shortcut (Windows)

• https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

sorry I am still confused what is safe mode? and what are add-ons? I have restarted it with add-ons disabled and i can see the internet pages ok so not sure i need these so called add-ons all i want to do is to look at websites in the middle of the page and have the toolbars at top to eg print etc

https://support.mozilla.com/en-US/kb/Safe%20Mode
"Safe Mode is a special Firefox execution mode that can be used to troubleshoot issues in Firefox. In Safe Mode, you can reset some settings or disable add-ons that might be the source of the issue. By comparing Firefox behavior in normal mode to its behavior in Safe Mode with various items disabled, you may be able to diagnose issues."

Any chance you have the Babylon Toolbar 1.1.8 installed?
If so, disable it to see if it is the cause of that problem.

hi I am still having problems in firefox as my add-ons are still disabled. I cannot see videos and eg 3d images of products on line. It prompts me to enable add-ons which are all disabled so should i just select all add-ons again? I don't know if I am still in safe mode so please advise what I should do to get add-ons back. Is there an easy way to re-start with add-ons enabled?