1. Press Cmd+N to open a new browser window, then type https://developer.mozilla.org/en-US/docs/Project:MDN in the address bar and press Enter 2. Inspect the subnavigation below the headline with the developer tool of your choice 3. See that a ordered list is used in the navigation. as the HTML spec says: "The ol element represents a list (or sequence) of items; that is, a list in which the items are intentionally ordered, such that changing the order would change the meaning of the list." this navigation has no specific reading sequence and the <ol> should therefor be replaced with a <ul> IMHO.  http://www.w3.org/TR/html-markup/ol.html
Making this block bug 910513 so that we consider it for the redesign. We even have the following link which does this automatically. http://mzl.la/mdn-redesign-feedback
My opinion is that the zone subnav's meaning would change if it were ordered differently. Those items are ordered the way they are for a reason. The same reason chapters are ordered the way they are in a book.