If you’re looking to run a multisite install of WordPress 3 and your hosting provider uses Plesk let me save you a little bit of a headache.
My Scenario
If you want to do a multisite installation i.e. run multiple blogs from a single database you basicly have two options subdomains or subfolders. Because I want to map existing domains to the child sites I was going to be setting up I figured that from a DNS perspective it would be much easier to go with subdomains.
Thus my blogs would appear as
domain.com
blog1.domain.com
blog2.domain.com
blog3.domain.com
Then I can setup CNAME dns records to point traffic from the desired domain to the child blog subdomain
abccompany.com -> blog1.domain.com