Got weird fullscreen ad when visiting website When I vistit on my nexus one the website alternativeto.net and open a subpage then suddenly I see a fullscreen ad with the title "liferay.com" and the address cat.m.ifortune.mobivillage.de

I see the desktop version of alternativeto.net when I visit them

Is it a problem of alternativeto.net or is there some virus on my smartphone?

It doesnt happen on other websites while surfing with my smartphone

if it is not android related, please move it to the right board (didnt know if i should post it in superusers?)
It has to be related to the website. It's possibly just a pop-up ad. 

Currently there's no known virus for the Android platform. There're other forms of malware but no viruses. Nevertheless you should always make sure to only install applications from trusted sources.