Google pinched to hit Adsense network next week.
Their machined are very good at the matching procedure, but there are still a few cases where their definition of significance varies from our human definition of relevance. In these few cases, the system might end up serving ads that don’t seem immediately relevant to users. We understand that increased ad relevance contributes to a positive experience for users, publishers, and advertisers, so we’re continuously working on ways to get better the relevance and quality of ads that appear on your sites.
For your information that this week; we’ll be rolling out a series of enhancements to AdSense’s background targeting capabilities, which will more accurately match relevant ads to webpages.
Based on this description, the changes may not affect parked pages. But one thing we know is that when Google makes changes like this, it usually means the company expects increased earnings from the changes, not to mention an improved user experience.