Thank you for the asnwers.
I wanted to use the random password for DB prefix as I wanted to make frontend creation as simple as possible. I wanted to force users only to give alias, title and chosing the tamplate.
If I use user_id I need to add site_prefix as well, to allow a user to create more sites stored in the same DB with more prefixes. In this case user need to provide a site prefix as well (for example a literature teacher who wants to create a wedding site will hard to understand what the prefix for).
Thanks for the alias explonation and example, I will try it. To be honest I did already, but as it is named "link" I have typed
mysite.com/{site_id} into the "Alias link" field.
Yes, the aim of the letter tree I understand I only haven't found anything about it in the documentation.
By the way, is it normal that using the letter tree the slave site cannot have it's own template color setup, if I disable letter tree than I can set up the template color of the slave site independently from the master? I think it shouldn't be different.
Jozsef