This is probably due to a problem with an add-on. For details of how to troubleshoot that see https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

Some AVG add-ons have been known to cause this problem.

i asked what to do, not what to read

No need to be rude. That link shows how to solve this problem.

so 659 solutions +1 link

If you post your extensions list then maybe we can tell which extension is causing it.

• Use the Troubleshooting Information page to help fix Firefox issues
• Help > Troubleshooting Information

The AVG Safe Search extension has been reported to cause this issue.

can you tell me my friend what to do with the avg? (yes i have avg) thanks

1. Click the orange Firefox button and select Add-ons to open the add-ons manager
2. In the list of extensions click on AVG Safe Search to select it, then click the Disable button
3. Restart Firefox

i apologize. i have avg programm, not the extension. i disabled ALL the extensions, i restarted firefox and the problem there is again. maybe considering re-install firefox 4?

ps. win 7 o.s