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I'm using a 2560 x 1440 monitor and Chrome. As you can see, the page background isn't quite able to fill the entire page.
I can confirm that you don't even need a ridiculously sized monitor/TV for this to happen. This also occurs on the much more sane 1920 x 1080 (24" 16:10 widescreen standard resolution for Windows)
Thanks for bringing this up. I cannot reproduce this issue in the current build of our network sites. If it remains a problem let me know!