The Sims Wiki is introducing a new feature called Miniboxes. Their purpose is to notify users that there's additional information available on the article they are currently viewing. It lets users know that there's a portal available, a userbox or that they can reach the page by typing in a shortcut in the search field.
Users are encouraged to help with adding miniboxes to all the related articles. Most of the edits required will probably be due to the userbox minibox which will need to put in all game articles and trait articles and so forth.
You can see the documentation for the minibox at its template page.
Note that the miniboxes aren't floating, they're merely aligned which means they'll position themselves next to any infoboxes instead of below them.