Board Thread:Support Requests - Designing Your Wikia/@comment-24424249-20150322025619/@comment-126761-20150323222031

The quick answer is: items may only be added to the right rail if they appear below the advertisements. Meanwhile, we generally encourage boxes to be placed at the bottom of the list.

We don't have a big list of "Do's and Don'ts" around these kinds of topics because we want to try and avoid ending up overly strict, and because both the site and opinions change over time - we like to be fairly reactive to user proposals and ideas, rather than proactively shut down all creativity.

Anyway, as a general rule: if any customizations affect the way advertisements display on the site, even if it's just moving them, it's not allowed.