In February Google, Yahoo, and Microsoft announced support for a new link element to clean up duplicate URLs on sites. The element is called the canonical link tag and the syntax is pretty simple.
This tag, added in the <head> section of an HTML page, tells search engines that the preferred location for the content of the request page is the value of the href attribute, in this case http://example.com/page. If you want to learn more about the canonical link tag, have a look at Matt Cutts' introductory post or Google Webmaster Central.
The new version of my Helperful Rails plugin provides a new method named canonical_link_tag, a super simple helper to generate the canonical link tag. The usage is similar to the auto_complete_link_tag helper.
canonical_link_tag
# => <link rel="canonical" href="http://www.currenthost.com/controller/action" />
canonical_link_tag(:action => "show")
# => <link rel="canonical" href="http://www.currenthost.com/controller/show" />
canonical_link_tag("http://www.example.com/product.php?item=swedish-fish")
# => <link rel="canonical" href="http://www.example.com/product.php?item=swedish-fish" />
You can install or upgrade Helperful via RubyGems.
$ gem install weppos-helperful --source http://gems.github.com