Canonical URLs from Google
Hallelujah, amen, and glory onto Google. They’ve finally addresses the issue of duplicate (or extremely similar) content with a rel attribute for the <link> tag.
Okay, okay, I’m backing up to explain. Let’s say that you have some content that is available via multiple URLs. Let’s say that you have example.com/page.php?id=123 that displays a review of a restaurant (or something similar). However, because most dynamic sites might also allow different sort and display options, this exact same content might also be available via:
example.com/page.php?id=123&catid=4
example.com/page.php?id=123&catid=4&authorid=3
Furthermore, the same content might be reached as example.com/reviews/restaurant/el-taco-loco. In the old days, Google, having discovered all these URLs, would simply assume that you’re up to no good by duplicating content. Whoosh, there goes you page ranking.
Starting this morning, you can add a <link> tag to the <head> section of your “duplicate” content, providing a canonical URL that Google will then treat accordingly.
<link rel=’canonical’ href=’http://www.example.com/reviews/restaurant/el-taco-loco’/>
Need more info? Check out the original posting over at Official Google Webmaster.
WP.Plugin: Canonical URL Wordpress Plugin.