MArcomage

This may not be possible and I know very little about computer programming, but is there a way to allow the site to adjust to the width of the window in which it's in? I'm playing on a 1920x1080 screen but would like it to occupy half of the screen. However it doesn't fit... (that's what she said).

You can adjust display of any web page in your browser (if you have Firefox or Opera). The process is not trivial, so I suggest that you use google to get detailed information about it.

I, for example, have a custom CSS for Youtube.

That CSS stuff is way over my head. I'm no programmer... :) I tried zooming out, but that makes things harder to read.