Blank page / Messed up page - Joomla

If somewhere the Accordion Menu would cause a blank page, in the backend or the frontend, then you should go to System (in Joomla 2.5: Site) → Global Configuration.

Go to the Server tab and pick Maximum at the Error Reporting.

Then go to the page, which was blank, and now it should write out the error. (You can ignore the Notice messages.)