That wasn't the problem actually: I always keep a file which isn't changed. I think the working with Mediawiki:sidebar did the damage, in combination with the change of monobook.php. Why it could not be reserved I don't know (I changed monobook.php back off course). What struck me before is that the JavaScript suggestions on the monobook.js page didn't work either. But if you have trouble with the navigation links in Firefox you know what to do. Rein