This excerpt taken from the PNC DEF 14A filed Mar 23, 2007.
You have the right to revoke your proxy. This right allows you to change your mind about how your shares will be voted at the annual meeting. You can revoke your proxy at any time before voting is declared closed at the annual meeting. You may revoke your proxy by sending a signed proxy with a later date in time for us to receive it before voting is declared closed, or by voting in person at the annual meeting. You may also revoke your proxy by using the telephone or Internet voting options explained below and on your proxy card. You cannot, however, revoke your proxy at the annual
meeting if you do not attend in person. You will not be able to revoke your proxy at the annual meeting if you listen to it through the webcast or teleconference options.
If your proxy is not properly revoked, we will vote your shares as indicated by your most recent valid proxy.