claus - 1:09 am on Feb 11, 2010 (gmt 0)
CNAMES for www.mydomain.com and *.mydomain.com to mydomain.com
Unless you use a number of subdomains the latter (*.mydomain.com) should not be needed.
What it does is to make sure that if I type, eg.
...or something similar, that your web site at "domain.com" will be displayed at this address. I can think of only few reasons why this would be desired.