Looks like youtube has updated their page again, and it it looks like I can't get rid of the white space at all...? I tried finding the color(s) through 'background colors' and it didnt work, so I got frustrated and just turned all foreground and background colors to black, with the 3rd shading option. STILL didnt get rid of white space, and in fact barely changed anything.
I just changed the colors on ebay's site to darker colors, so I don't think its my firefox, or color that site add on glitching.