Where is the css to edit?

[doug1]

I'm trying to edit the css for forum posts.

When I use Firefox's "Inspect Element" I find that the content of the posts is styled:

<blockquote class="postcontent restore">

I'd like to edit the css line:

blockquote {overflow:hidden;}

but I can't figure out where the css sheet I need to edit is.

Could someone help please?