Simplify Wikipedia's layout by hiding the menu (still expandable via button). Also works on most mediawiki wikis.
How many times have you actually used wikipedia's left hand side menu? Not that many, huh?
Get rid of that dead space with this extension and enjoy your content in full page width!
It will collapse the wikipedia and other wiki's menu for you, hiding it by default, while still leaving it accessible through an icon, in case you do ever need it. To show the menu, click the menu icon on the top left corner.