If you check the "www" box, Plesk sets up the server as
www.example.com. It also adds an Apache config entry so that all trafic to example.com gets redirected to
www.example.com.
My problem with this is is that it now appears in the browser address bar as
www.example.com, and I decided that if it was going to rewrite the URL, I prefer to have it rewrite the "www" to the version without the hostname, in other words, do it the other way around.
So, I set up my domain without checking the "www" box. Then I added this to the end of httpd.conf:
ServerName www.example.com
RedirectPermanent / http://example.com/
Where ip.ip.ip.ip is your server IP address.
Now, everything redirects to the bare domain name. Basically, the reverse of the way Plesk does it.
Ideally, I'd prefer to have it work without rewriting the URL, but I haven't had much luch using the ServerAlias directive, which is supposed to accomplish this.