I bring along my firefox with my USB thumb drive. Some people asking me, why I need firefox? Ya! Why I need firefox? I don’t really have a good answer for it.
My reply to open source users, firefox is open source software. For normal users, who cares!? Answer for normal users is, I like the dictionary plug-ins for firefox.
There is a few dictionary plug-ins available for firefox, earlier I am using a plug-ins connect to Altavista babble fish service (the plug-ins should be here), now I am using oak vocabulary plug-ins.
It is quite powerful, you can configure to activate the dictionary service as a tooltips, and you can configure and add in different online dictionary services.
This is the reason which is good enough for normal user to use firefox.