mcavic - 7:55 pm on Feb 17, 2009 (gmt 0)
This is going to go right over the head of 99% of webmasters.
What's so hard about it? You have multiple URLs showing similar content. You want the users to have access to the multiple URLs, but you want search engines only to index one of them. So you stick a tag on each page pointing the SE's to the official URL.