Szia Csaba,
This sounds crazy and I don't know if the link:
http://www.szentkereszty.net works from my home now, but I just tested through the high security firewall of my employer and the link works. Yesterday when I read your post the first time I was logged on the same network through the same firewall...
Hm.... this is weird indeed because normally the opposite is expected, some links should/may not work from my work place but work from home.
I don't know if it helps you solving the issue you have with your ISP, but it is sure strange.
Though one thing is as expected... the link:
http://kredenc.onmypc.net/net/uccnc_quickview_plugin/index_en.html is blocked by my company firewall, and that is no surprise for me looking at that web address.
I just thought you wanted to know.
Köszi a programot, este kipróbálom.