<<We're now requiring AdSense publishers to comply with the spirit of our Page Quality Guidelines (http://adwords.google.com/support/bin/answer.py?answer=47884&sourceid=aso&subid=ww-en-et-asblog_2007-06-05&medium=link)>>

More here: http://adsense.blogspot.com/2007/06/policy-updates-and-its-not-even.html

If you have pages that not comply with the guidelines, you aren't accepted in Google AdSense program.
So what's new?

This line:

<< Publishers using online advertising to drive traffic to pages showing Google ads must comply with the spirit of Google's Landing Page Quality Guidelines. For instance, if you advertise for sites participating in the AdSense program, the advertising should not be deceptive to users. >>