Adding MIME type to Firefox

Here is what happened, i was trying to make the rar files get saved without a confirmation, i click the file, it gets saved without asking me, simple? isn’t it?
It turned out that it’s not, Firefox ,sadly, when you choose "Do this automatically for files like this from now on." it simply doesn't, you have to add the RAR MIME type by your self, well, here is how
The following procedure can be to add MIME type for file extension. Please edit a file carefully

1. Quit Firefox completely.
2. BACKUP mimeTypes.rdf in your Firefox's profile folder
3. Open mimeTypes.rdf in your Firefox's profile folder by text editor
4. Find line of
   
5. Insert the following code AFTER line which is found in step4.
   
6. Find line of .
   
7. Insert the following code BEFORE line which is found in step6.
   
8. Save mimeTypes.rdf (should not change character encoding).
9. Restart Firefox

that’s it, now go to Tools>options>applications , and you’ll find the new RAR MIME type available, your call, enjoy

ref:http://forums.mozillazine.org/viewtopic.php?f=9&t=1706945