Like a sound site architecture and directory structure, product categorization can play a significant role in how both search engines and users are able to access your products. There are two important things to consider when determining how to categorize your products. 1) Is each product assigned to the most appropriate category or categories? and 2) is multiple categorization creating duplicate content? The first issue frustrates your users and the second the search engines.
Looking for examples of both of these I found exactly what I was looking for on The Home Depot website.
Improper Product Categorization Frustrates Shoppers
Below you see a screen shot of a book that I found under the Electrical category. If you look at the breadcrumb you'll see that under Electrical there is a sub-category of "Books and DVDs", which is, appropriately, where this book was found.

My first thought here was that The Home Depot needs a section devoted entirely to Books and DVDs. That will give their users access to their full library of books rather than just a few at a time, depending on what category they are in. I found a pretty large selection of books (44 titles) in the Tools and Hardware section of the site, yet the book above wasn't listed here at all. Having a dedicated books and DVDs section would save visitors a lot of time searching.
But more to the point here, this book in particular could NOT be found where I would most expect it to, in the Decking section. Granted, a deck and a patio may be completely different in technical terms, but to the layman like me, a deck is just a patio higher up off the ground.
I would think that if the above mentioned book was found in Electrical, surely it would be appropriate to link to it from Decking. But the decking page has no links to any books or DVDs that many of the other categories have.

Why not? This category links to hardware and parts for a deck, why no how-to?
The goal of categorization of your products is to ensure that any product can be found where a customer is likely to look. The great thing about the web is that products don't have to be placed in a single place, in a specific isle. Through multi-categorization, they can be found from any relevant isle (web page, category, etc.) When categorizing your products it's important to think in the terms you customers might. Don't rely on someone knowing the difference between a deck or a patio.
A similar issue can be found when looking for an electric lawn mower. I might consider it to be a power tool. (I'm a computer guy, what do I know about power tools and lawnmowers?) but it's not there. The Home Depot needs to make sure their website speaks to outdoor dunderheads like me.
Improper Product Multi-Categorization Frustrates Search Engines
Let's move on to multi-categorization, and how it can often lead to duplicate content. Our book example above is perfect. In the image above I've provided the breadcrumbs and the URL. But look here, the same product can be found in an entirely different category. That's not a bad thing, but the problem is that the URL for the product is completely different:

What Home Depot has done here is created a completely duplicated page. Lo and behold, this same book is also fond in the Concrete section of the site creating yet another duplicate page. Amplify this with just a dozen products and a dozen possible relevant categories for each, and you're looking at almost 150 duplicate pages. More products and more categories only amplifies the situation further.
But it gets worse here for The Home Depot. They have an entirely duplicated category:


Not only are the listing of products in each category duplicate of each other, but that every product linked from these pages is also duplicated, each with their very own URLs.
With duplicate pages like this, the search engines tend to slow down the spidering of the site. That, and some product pages may not get indexed at all, either because many duplicate pages are dropped, or the search engines stop spidering duplicate categories, some of which may contain the only link to certain products. No matter how you look at it, you're leaving to the search engines to do a lot of extra work they'd rather not do. Simplifying your product categorization will ensure more products get spidered and indexed and valuable products won't be left out.
A couple of side notes I'd like to make: in the two images above, look below the orange "add to cart buttons". The text beneath is different. One it's telling you to "check your local store" on the other it tells you it's an "online only" purchase. Confusing.
Also, one of these categories shows more products than the other.

This lends back to issue number one above, with products being categorized properly, but also to the issue of duplicate categories. If the search engines decide that the category with more products is too closely duplicated with the other it might choose not to index or follow the links at all. This could leave these additional products left out completely.
This article is a continuation in my series on duplicate content. Follow the links below to read more:

Stoney I have used HD for clients on examples on how not to do things fro years. The whole website is mess. I cant believe they have not hired someone to help them out.
Hey, there is something to be said about knowing where to go to get good examples!

$100 in Free TLA's!
Increase your traffic and link popularity.
SEO Courses Online
Tutor-supervised or self-study options
Cheap Submission Services
Quality SEO services, dirt cheap prices.

Sage not only personally invites you to come hear him speak at Search Engine Guide's upcoming Small Business Marketing Unleashed Conference, but he also reviews some of the show's best features. He highlights the top of the industry speakers, the wide array of in-depth topics to be covered and the appropriate, yet really fun conference location.
Search Engine Guide Blog | Search Engine Marketing | Internet Search Engines | SEM Resources & Consultants | Newsletters | Advertise | About | Site Map
Search marketing information for small business owners.
Fetching the best small business news.
A friendly place to share small business ideas and knowledge.
A different kind of small business marketing conference.
Home of our network.
Copyright © 1998 - 2008 K. Clough, Inc. All Rights Reserved. Privacy
FreeFind Site Search Engine - FreeFind adds a "search this site" feature to your website, making your site easier to use. FreeFind also gives you reports showing what your visitors are searching for, enabling you to improve your site. FreeFind's advanced site search engine and automatic site map technology can be added to your website for free.
(Unpaid placement - FreeFind is a Search Engine Guide partner.)