I have now tested with another PC and it works. With IE and Firefox. There seems to be a browser problem.
Thank you for your efforts.
This link opens a Windows and a pop-up:
<a href="http://193.47.122.27/webcam/cam3_vlz1.jpg" class="popup"data-height="350"data-width="365"data-scrollbars="0" alt="my link text">A1 Mägenwil</a>
This link is OK:
<a href="http://images.webcams.travel/original/1049027676.jpg" class="popup"data-height="300"data-width="300"data-scrollbars="1" alt="my link text">Aarau Bahnhof</a>
