I just found out about them.

Do you use Firefox Personas? :D

I use the one called "Firefox B"

http://www.getpersonas.com/gallery/All/Popular

THEMES FO LYFE.

Seriously, Personas f*cking suck.

i use the then
the one i currently have has the firefox logo on it

What do they do and how do they work.

They just change the look of the normal firefox
browser
It makes it look much nicer

I think they're fun. I think it lets you make your own custom ones.

*goes to check*

edit:

Yes, it does. There's a link at the top of the page.