A new change in the display URL policy has been declared in the official Google Adwords blog. The change will take place in the policy for URL’s displayed for the ads that lead to hosted domains. The sub-domain part of the domain needs to be displayed along with the main domain.
This policy can be understood with the help of an example. Let’s say if the URL for the AdWords blog is http://adwords.blogspot.com, then in that case, the display URL according to rules should be adwords.blogspot.com and not just blogspot.com. This change applies to all URL's.
The change in the policy is meant for all the hosted domains and should be applicable to all of them.