The joomla article url's show the article id, the category and the section. This leads to canonical issues whenever the section or category changes. Same problem when a section/category menu is added or a site switches from non-SEF to SEF url's.

 

The article canonical plugin will put a canonical link in the header of the document, pointing search engine's to the right location:

 

http://www.affiliatefeeds.nl/en/46-general/3060-quick-guide.html

 

<link href="http://www.affiliatefeeds.nl/en/47-datafeeds/3060-quick-guide.html" rel="canonical" />

 

Joomla 2.5

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Joomla 1.5

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Joomla 3.x has its own canonical system.