On which page does it occur? What is the exact message?

It is a slow script warning to prevent the browser from becoming frozen.

ok the last one was chrome://vidbar/content/downloader.js:107 and i think it usually happens in facebook

also my firefox goes not respoding lot laterly..

http://static.ak.fbcdn.net/rsrc.php/v1/yW/r/WadHodw9vHf.js:57 this one is from today. again in fb

1) The script warning is coming from the 'vidbar' extension - you should check with for an updated version. You can disable it for now and see if the issue persists

2) Is you are getting regular not responding messages try http://blog.bonardo.net/2011/09/30/is-your-firefor-freezing-at-regular-intervals

This issue can be caused by an extension that isn't working properly.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration 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

"Script: chrome://vidbar/content/downloader.js:107"

This is exactly what my problem is - and you write that the script warning comes from the vidbar extension which I should check for an updated version! But I hate to tell - but I don't know what my "vidbar extension" is and therefore I don't know how to update it!! Sorry :) Hope you can explain it better for an non pc wisard :)

usually it happens on facebook....

i have changed a theme and almost never have problem again..