User blog comment:Kirkburn/Technical Update: March 3, 2015/@comment-24312789-20150304145731

Ehmm, I am afraid the normal "Desktop" preview does not work properly. It shows the page in incorrect width, it is thinner than it is supposed to. I am using Firefox, if anything.

BTW, aren't this "Mobile" and "Desktop" buttons kind of huge? Wouldn't it look better, and more consistent with the rest of the options if they were the same size as buttons under "Add features and media" and "Templates" categories? This way you could actually make "Changes" and "Publish" buttons as well and simply put them all in one line.