[DJDD]

I get the same error message.

The link in your post redirects to:
www.teleskop-express.de/shop/product_info.php/language/en/info/p641_Off-Axis-Guider---nur-9mm-Baulaenge---T2-Anschluss---fuer-CCD.html
with http:// in the front, of course.

even the base URL:
http://www.teleskop-express.de
gives the error