¿? Did you tried to do it yourself first?
This is for Kde:
Select an *.html file, right click on it.
Press the wrench pic , then press "add", select Mozilla, or in case you dont know this is the command: mozilla %u .
Then Move Mozilla to the top.
Press Apply.
Done.
Gnome should be similar.
You should really read "How to ask questions the smart way"
Plus, what is this:
http://www.linuxquestions.org/questi...hreadid=236012