If I want to make a firefox extension

Where would I look, (as far as tutorials)
and what would I need knowledge in in order to make a firefox extension?

please and thank you for the help

 

I think you should start reading this page

http://developer.mozilla.org/en/docs/Extensions

 

think they are java based.....

 

javascript,xml and css...

 

thanks, ive decompiled some extensions just to see what they are made of and mostly it seems to be javascript / css , but i wonder how advanced it is and stuff, im really good with css / php but have never really gotten the hang of javascript..