Hey, thanks! That does the trick, it instantly worked. Again, thanks.
Got any info regarding the global search and search for category questions I also had in this posting?
Also, another question, that I forgot to write down: How can I make use of the plugin Shopper Info? As I see, this will be necessary if anonymous are allowed to shop. But the documentation of this plugin is a little... basic. The interface is described, but no examples are given, nor can I find any elsewhere on tiki.org. How do I collect the basic data like name, address, zip, city, country etc and in a way that it does not collide with the data that is available for registered users? After all I will need this to write some code that could build the invoice.