Sometimes the choices someone else did in their CSS does not suit you. Often, you give up, never to come back to their site, or fiddle with the size of your browser window. Using Firefox and its [Developer Toolbar](http://chrispederick.com/work/webdeveloper/) extension by Chris Pedrick, I have now gotten around to using my own stylesheets (with small changes in them) on websites I use a lot.
These two steps show how I added my own width to the website The Forge, which is full-screen wide.
First, create a CSS stylesheet (what I did what set the rule `body { width:660px; margin:auto; }` in a little CSS file, and save it on my computer where I can easily find it. (You can use the one I use: download it here).
Turning on the CSS file for a page is done like this:
Persisting to use that CSS file is done like this:
Not that it is helpful here, but Microsoft has developed a pretty neat developer toolbar as well (beta, though):
Unfortunately it can’t disable or change style sheet, but if one is trying to debug a page that looks weird in IE, this toolbar is a must, just as the developer toolbar is a must in Firefox.