Could adding canonical tags to large Ecommerce site ever hurt rankings? Temporarily?

[iAnalyst.com]

We have a really large site we're working on who's product pages rank well for the most part but also have multiple products listed in different categories with different URL's. I'm assuming there's no downside to adding canonical tags to these right? Its peak season so I don't want to do anything that could, even temporarily, bring down their rankings.

Thanks!

[Hurf]

Have you actually created duplicate product pages (under different categories) - which is how it sounds to me?

Or do you have the facility within your ecommerce package to display a single product across multiple categories?

(I have ecommerce stores powered by Interspire and they allow the product - www.mydomain.com/products/product-123.html to be contained in multiple categories So you can drill down and find this single product page under 2 or more categories - without the need to create duplicate product pages.)

If you use the rel=canonical tags, only the page/s the canonical link points to will get indexed (if you have created the duplicate products) - is this what you want?

How do you decide which product remains in the index if you use the canonical tag?

Can all of the duplicate pages be dropped from the  index without causing too much of a problem - based on your current architecture?

Are you currently getting penalised or indexed for the duplicate pages?

It would be good if you could map it out step by step (as it is setup now) and then clearly state your goal i.e. We currently have www.shopdomain.com/category-TWO/identicalproduct1 and www.shopdomain.com/category-TWO/identicalproduct1 and we only need to index www.shopdomain.com/category-ONE/identicalproduct1?

Let's see if we can't get you some solid pointers to resolve this.

[firstconversion]

well, no downside if you do it right. Ive seen (and been part of!) when you do this type of thing on a large site via automation and don't realise all the implications of where you are redirecting. When you start doing this stuff, you appreciate what people mean when they advocate KISS

You may well experience changes to indexation etc as you are effectively changing the flow of PR through your site and its pretty hard to know what the effects will be beforehand on a large complex site

Make sure you have a good view on your analytics & try this on a smaller part of your site and see what the effect is (if you can)