Google has recently made a change to its display URL policy on it’s paid search ads. Google claims this has always been its policy however it has seldom been enforced. The new rules will require a ad’s display URL to match the destination URL. So for example: a display url of www.somewebsite.com must land the user who clicks on the ads to the somewebsite.com website.
Advertisers are still allowed to send users to either a subdomain foo.somewebsite.com or a subdirectory somewebsite.com/foo/foo.html. Google claims this policy is in effect to minimize any surprise or confusion on the surfers behalf if they land on a website not listed in the display url.
For now all ads currently running will not be disapproved unless a complaint is filed or Google is notified about the directly. However all new advertisers or new ad placements will need to comply to these new restrictions.