It seems I've done womething wrong in the configuration of an individual website in my DNN-portal.
When I'm loggen out, and visit my website by it's URL, I still see the editor's panel on top of the webpage. I can expand or minimize it with the arrows on the right, but I can't make it disappear entirely.
I've got another website in the same portal, but there everything works perfectly. I just can't figure out what's the difference in configuration between them.