Heureka. I found it.
What I have done… Maybe it is usefull for someone else…
The different between the working pages and the “bad” pages were, that in the “bad” ones were widgets in the sidebar at the right.
After finding the 3 errors with the Javaconsole created by the facebook javascript I tried to eliminate this errors. I have had to control the widgets, because here the javascript was called. But this was not the error. So I decided to stop all widgets. I have done this with the menu for the widgets in the admin area of wp. Nothing, error remained. One widget I wasn’t able to cancel. The counter from blogcounter.de. The blogcounter was called with a small script in the sidebar.php. I disabled the counter and all were working well. The solution at the end was, to get a new script from the website of blogcounter.de to embed the counter.
Hope I was able to describe it well.
Thank you very very much for your kindly and quick support Richard.
And nice greetings from Italy ??