Why does my domain works on domain.com but not www.domain.com?
When adding a domain in plesk, there is a tickbox to add the 'www' prefix on domains.
If this is not ticked, and you attempt to view your website in a browser it will only work like this:
http://domain.com
and not http://www.domain.com
If your domain has only just been added, the easiest way to correct this is to:
Log into plesk
Click domains
Tick the box next to your domain then click remove (make sure you have any content backed up before doing this)
Click create domain and make sure the www box is ticked
If you have already uploaded all of your content and do not want to have to re-do it. Please use this method:
Log into plesk
Click domains
Click on your domain
Click DNS settings
Make a note of your settings
Click restore defaults
On the box that pops up make sure you tick the www box and click ok.
This change could take 2-3 hours to take effect but once the change is
live you will be able to access your domain on both http://domain.com
and http://www,domain.com