Firefox 8.0

Thanks for a prompt response. It wasn't working for me in the morning, when I set the "browser.showQuitWarning" to "true". I was using firefox for the whole day with many tabs opened and after your response I have tried again. Browser has been closed without any wornings, but when I have start it again all tabs were present, so looks like it is working now. I have no clue why it wasn't working earlier.