I just realized that my page is also accessible when there is a .html extension on the url.
The url would be: http://musikwerkluzern.ch/programm
but http://musikwerkluzern.ch/programm.html works as well but some tags are not being rendered with the html extension attached.
And for some reason the google search results link to the page with .html attached.
That's bad. How can I prevent this? Is this a