Most pages under 'settings' show an unnecessary and ugly horizontal scrollbar at the bottom of the screen, tested in Chrome and Firefox (In Chrome always, in FF only when the screen is less than about 1500px wide, but still).

This is caused by the -15px in this CSS:
.admin h2 { margin: 15px -15px 20px 0; }

It makes the h2 stick out of the window. If the -15px has to stay, then it can be fixed by:
body { margin-right: 15px; }