What have I done wrong

I got this e-mail, can someone tell me what I done wrong

"

Hello,

After reviewing our records, we've determined that your AdSense account
poses a risk of generating invalid activity. Because we have a
responsibility to protect our AdWords advertisers from inflated costs due
to invalid activity, we've found it necessary to disable your AdSense
account. Your outstanding balance and Google's share of the revenue will
both be fully refunded to the affected advertisers.

Please understand that we need to take such steps to maintain the
effectiveness of Google's advertising system, particularly the
advertiser-publisher relationship. We understand the inconvenience that
this may cause you, and we thank you in advance for your understanding and
cooperation.

If you have any questions or concerns about the actions we've taken, how
you can appeal this decision or invalid activity in general, you can find
more information by visiting
http://www.google.com/adsense/support/bin/answer.py?answer=57153.

Yours sincerely,



The Google AdSense Team"