Install firefox add-ons from local disk

[yk]

> One of the options (if the addon is an xpi) is to do a file -> open and 
> locate the file and that should fix it.


> They're supposed to be in .xpi format, not .jar 

I thought theme is a kind of those addons.
sorry

> Also have a look at MR Tech [1]
MR is just the right thing I'm looking for,it at last gives me a 
"Install" Button~~

Thank you guys very much!!