currently the project player is usually 404 pixels tall (at least on my system), and because projects generally don't actually have this size many things look worse on the community page, especially my cube project because of the pixel aligned stamping
EDIT: the current project there now looks fine on the community page because i changed the stage size as a fix for now, it had dark vertical lines on it before
i think the site should be modified to make the window try to match the actual project size or smaller, i don't think it should ever be larger, except in fullscreen