You can modify the pref keyword.URL on the about:config page to use Google's "I'm Feeling Lucky" or Google's "Browse By Name".

• Google "I'm Feeling Lucky": http://www.google.com/search?btnI=I%27m+Feeling+Lucky&ie=UTF-8&oe=UTF-8&q=
• Google "Browse by Name": http://www.google.com/search?ie=UTF-8&sourceid=navclient&gfns=1&q=

• http://kb.mozillazine.org/Keyword.URL
• http://kb.mozillazine.org/Location_Bar_search

Thanx for ur reply....But when I'm typing a website name e.g "google" in address bar its not opening google main page it opens google in google search. In firefox 3.6.12 when i type website url without .com and press just "enter" it directly opens a main website whether it is google, facebook or youtube.