I always forget how to get into maintenance mode on Sharepoint pages to close / remove webparts that are (potentially) causing issues. Sometimes you will even get an error message that provides a link to the maintenance mode pages. There is also some convoluted way of getting into maintenance mode, but I can never remember it.
An easy way to get into maintenance mode is to simply add ?contents=1 to the URL. For example, if your URL was http://sharepointsite.com/pages/default.aspx you would go to http://sharepointsite.com/pages/default.aspx?contents=1