That's because there's no GWT Development Mode plugin for Firefox 14. And now I can't work!
Wait! There's a solution. Instead of fighting with ubuntu with reversing installed Firefox to 13. I can have parallel versions of FF.
So how to install previous version of Firefox on ubuntu?
and download your binary. Be cautious with 32 and 64 version. If you don't know what version do you have, call
and it'll tell you.
Then unpack your version to desired directory (other than current Firefox's dir).
Close any running Firefox instances and run your downloaded version. Beware of upgrading both firefox and any plugins. Don't do this. This copy should remain as is.
If you're looking for unofficial GWT Development Plugin versions (for FF12, FF13 and soon for FF14) you might looking at my gwt entries.