If a website visitor is using a Mac for visiting grml.org we might present him the 
according installation instructions for USB (based on e.g. http://wiki.grml.org/doku.php?
id=usb#building_an_efi_usb_key_on_a_mac) on the download webpage. Same for Windows, 
Linux,...

The USB installation should be dead simple for the user and since we even provide that 
technically we should just improve the documentation and provide it to the user in a nice 
and decent way.