While I personally never had difficulties with Firefox's built-in offline mode and automatic state switching to it, I have had contact with users who reported that this happened regularly in their version of Firefox.
Firefox switches to offline mode if it cannot detect a connection to the Internet. This can happen on startup or at any time when the browser is running on the system. Some users mentioned that Firefox would switch to offline mode automatically even if an online connection was available at that time.
We have previously mentioned how to prevent Firefox from entering work offline mode by adding a hidden parameter to the Firefox configuration. Not every user on the other hand is comfortable editing those settings in the browser.
Those users can now install the Firefox add-on StayInOnlineMode for the very same effect:
Firefox 3.5+ might start in offline mode if there is no net connection available. While being in online mode even short connection interruptions can also cause Firefox to switch to offline mode. If you frequently run web applications unattended, then unexpected switching to offline mode can easily break the workflow. This small addon forces Firefox to stay online while still allowing a user to manually switch to offline mode if required.
The extension keeps Firefox online all the time and prevents any attempt to switch to offline mode. The only option to switch to offline mode is if the user initiates the change manually from the Firefox menu.
The add-on is compatible with all Firefox versions starting with Firefox 3.5 and including the latest builds of Firefox 4. Firefox users who experience regular automatic changes to offline mode may use the add-on to prevent this from happening.
Update: The Stay in Online Mode add-on for the browser has been removed by its author from Mozilla's Add-on repository. There does not seem to be a comparable extension available at this point in time.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.