Thnks for the responses.

Richard & NTDOC; as for the other possibilities to open new window or to type in the URL in the windows explorer, you are right but how can i say it in gentle words. 99% of the users in the branches are "dumb" as it goes for manipulating or using Windows OS. They are suffering from a great lack of using the OS, they only now what they have been taught. So in my case disabling the address bar will work quite well [i hope]:-)

Anyway, i will try MART link and the Content Advisor, worst come to worst i'll go for the FW which i know i can do it over there but it's quite complicated since in every branch there is a manager computer which should be allowed to surf all sites.