If you login to Google Webmaster Tools, click on site configuration, then on settings, you will see a new option for "parameter handling." Here is a screen capture:
This basically allows you to tell Google which parameters in the URL they should ignore. This comes in handy for tracking parameters added to the URL, or duplicate content caused by printer friendly URLs and many other cases.
If you want to learn more about how this stuff works, see the Google help document or read Search Engine Land article. Also, Brain was the first to spot this.
I posted a thread on this topic at Google Webmaster Help where a Googler, Jonathan Simon added, "One small correction should be noted in regards to the Search Engine Land blog post where it says it's okay to mark parameters that control sort order as ignorable. That's only true if the sorted results all fit on a single page. Otherwise you could unintentionally be excluding some data."
Yahoo Site Explorer has had this feature for a while now. Yahoo calls it Dynamic URLs and the screen looks like this:
You can learn more about Yahoo's dynamic URL feature over here.
Forum discussion at Google Webmaster Help and WebmasterWorld.
