13.1.3. The canonical tag
One frequent point that SEOs raise is the so-called 'duplicate content penalty'. The claim is that having a page accessible with multiple URLs will harm search engine ranking, or even (according to some SEOs) have you booted from Google for spamming.
In reality, as the official Google blog makes clear (see link below), you will not be penalized for this. In fact, Google will even do a good job of recognizing multiple URLs that point to the same page, pooling them and their page rank.
http://googlewebmastercentral.blogspot.com/2008/09/demystifying-duplicate-content-penalty.html
But in order to eliminate any doubt, Google, Microsoft (Bing) and Yahoo all now recognize the 'canonical' tag. This lets you specify within the source of a page which URL that page should be indexed as. So even if it is reachable through multiple navigation routes, you will tell Google the preferred URL to use. Kartris forms canonical links automatically within pages, so you don't need to activate anything in this regard.
Google's official position is that it takes the canonical tag as a strong hint, rather than obeying it absolutely.
13.1.3.1. Why doesn't Kartris use 301-redirects instead?
301-redirects were commonly used as a method of getting the preferred URL indexed by search engines prior to the canonical tag being introduced. The problem with using 301-redirects is that it loses 'location awareness' in a URL. For example, a product 'laptop' can be in multiple categories, and the folder hierarchy in the URL will be different for the same item depending on the route you use to navigate to it.
Using 301-redirects means that end users, as well as search engines, only get to see a single URL, and therefore lose location awareness through the hierarchy and breadcrumb trail.
Using the canonical tag is better because it allows us to pass location specific information through the URL, giving users a clear idea of where the product lies within the category structure, while at the same time notifying search engines that it is a single page, with a preferred URL.