Google has just recently released a new type of <link> attribute. It's the rel="canonical" attribute. This attribute is used to specify a preferred domain, so that Google bots don't penalize you for duplicate content. To use this, simply place the following code into your head section: <link rel="canonical" href="PREFERREDURL" /> Code (markup): This is very useful for dynamic sites and forums. For example, you can access the 'Google' forum here through these URLs: http://forums.digitalpoint.com/forumdisplay.php?f=5 http://forums.digitalpoint.com/forumdisplay.php?f=5&daysprune=-1&order=asc&sort=title http://forums.digitalpoint.com/forumdisplay.php?f=5&daysprune=-1&order=desc&sort=lastpost http://forums.digitalpoint.com/forumdisplay.php?f=5&daysprune=-1&order=desc&sort=views http://forums.digitalpoint.com/forumdisplay.php?f=5&daysprune=-1&order=desc&sort=voteavg and many others... Now, this is just a duplicate content disaster waiting to happen. So what do you do? You simply place <link rel="canonical" href="http://forums.digitalpoint.com/forumdisplay.php?f=5" /> into the head tag of this forum, and Google bots won't index any URLs but that one. Read more here: http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html PS: I believe this also solves the whole /index.php dilemma
When I first read the name of this, thought it was something completly different. Have fun updating! (How long till Yahoo follows suit?
Google is not the only one who contributed to this feature. Yahoo and MSN also collaborate on this. http://www.mattcutts.com/blog/canonical-link-tag/