You can check if you have an user.js file in the Firefox profile folder that sets the browser.sessionstore.resume_session_once pref to true.

• http://kb.mozillazine.org/browser.sessionstore.resume_session_once

• http://kb.mozillazine.org/Preferences_not_saved

Türkçe yardım alabilir miyim?

I do not read or write Turkish and used Google Translate to translate your question.

• http://translate.google.com/?hl=en&ie=UTF-8&sl=auto&tl=en&text=

Do you have a user.js file in the Firefox profile folder?

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

If you have then you can delete this file.

Note that Windows hides some file extensions by default.
Among them are .html and .ini and .js and .txt, so you may only see a name without file extension like user in this case.
You can see the real file type if you open the Properties via the right-click context menu

I just couldn't find the "Help". Sorry.

You should find Help under the Firefox menu button drop-down list and via the File menu.

• Press the F10 key or tap the Alt key to bring up the hidden "Menu Bar" temporarily.

• https://support.mozilla.org/kb/how-do-i-get-firefox-button
• https://support.mozilla.org/kb/Menu+bar+is+missing

See also:

• https://support.mozilla.org/kb/Preferences+are+not+saved

I deleted the file and reseted the firefox.

It just stopped saving the last session everytime but it still not openning my home page when I open firefox. It opens http://www.qvo6.com/?utm_source=b&utm_medium=mlv&from=mlv&uid=SAMSUNGXHD502HI_S1VZJ90S740244&ts=1374531183 instead. How to get rid of this?

Try http://malwarefixes.com/remove-qv06-com/

Merhaba, Ayarlara girin (about:preferences sayfası), ilk açılan sayfada "Firefox açıldığında:" Seçimini görüceksiniz. Orada Ana Sayfamı Göster seçmeniz yeterli.