Domain without www not working from plesk hosting

I use plesk hosting for my company. An error I got (and shocked with it!) was that my domain was displaying the correct site with :

http://mysitedomain.com

But did not work with:

http://www.mysitedomain.com

Later it was traced that, by default the www was not included while creating the domain.
So if you are creating a domain, don't forget to inlcude www (by checking a checkbox next to www). That will keep yourself away from the worry.
If you have already created the domain and have the problem, you can always go and edit the domain (from the very first page that lists all the domains) and update it to include www.
Cheers!