As I entered the forum tonight, I saw this banner (see upper circle in image) and when I stopped the mouse just over it, I realised the link was pointing nowere (see bottom circle in image)... I guess it should point to wiki.simutrans.com :P
(http://www.simutrans-germany.com/files/upload/wiki_link.jpg) (http://www.simutrans-germany.com/files/upload/wiki_link.jpg)
As this topic is about a forum issue, I moved it to "Simutrans forum and site" board.
I found the problem:
[center][url=http://http:\\wiki.simutrans.com][size=4][b]Do you need a help?[/b][/size][/url]
Simutrans Wiki Manual can help you to play Simutrans. Now in 6 languages.[/center]
... and now it's fixed.
Thanks. :)