In Ubuntu Hardy Heron, firefox always open in offline mode. This is really very annoying.To open firefox always in online mode do the followings :
1. Open firefox
2. In the address bar type the following and then press enter
about:config
3. In the filter bar paste the following :
toolkit.networkmanager.disable
4. Double click on it and make its value to “true”.
5. Restart firefox.
Now firefox will always open in online mode.