Hello, Texas Infidel,
You can probably change it within your blog’s stylesheet. WordPress allows to edit (in Appearance) those things, including the style.css stylesheet.
Typically, your theme contains a div block designed to contain everything of the blog, and it has been assigned a width in the stylesheet. Change that width, you change how the blog looks.
I don’t know how to do it with Firefox (been told it’s now doable even without firebug, beats me how), but I know that with the developer tools provided by Chrome you can live edit a styleshee and see what’ it’s doing…
(Yeah, sorry I don’t give you an already-ready answer, but I promise, it’s worth investigating, it should liberate you to find how to do it, it’s really not hard ?? )
