Where to specify StyleSheet in Firefox

[Kent West <westk@acu.edu>]

I thought Mozilla allowed one to specify a custom stylesheet, and yet 
I'm finding no option for that in FireFox. Am I missing something? I did 
a google and went to the FireFox Extensions page and searched fro 
"style", but didn't find anything that really looked promising. EditCSS 
looked the most promising, but the description doesn't sound like the 
user tool I thought Moz browsers had.

Perhaps my understanding of custom stylesheets is faulty; I thought you 
could create a local stylesheet (or several), and then specify FireFox 
to use that stylesheet for rendering custom versions of HTML mark-up, 
like custom versions of the <H1> tag, etc.

--
Kent