Large sites have a variety of problems. They are inherently more complex than smaller sites to manage from many perspectives. Some of the major ones include:

1. Content management is a major challenge
2. Providing users a quality user experience (e.g. an easy to understand navigation system) may be difficult
3. And, yes, SEO can be a challenge too

One of the most common SEO problems relates to managing complex site hierarchies. An example of this is when you try to implement a site with a local aspect. For example, let’s say you sell widgets, and like pizzas, it matters where you sell them. Let’s also say that you sell widgets in 200 different cities and towns. So far it’s not too bad.

Now let’s complicate things a bit further and imaging that there are 45 different types of widgets (e.g. you sell auto parts, and there are hundred of different types of parts), but there is still a reason to be concerned about where you sell these widgets – perhaps there is a service aspect to it, or some reason why the customer wants to be able to look at the actual product first.

Now you decide you want to offer your users the navigation of their choice. Want to search on the product type first? Go ahead! Pick widgets, then blue widgets, then pick the city where you want to shop for it. Your breadcrumb bar might look like this: Widgets > Blue Widgets > CityName. Pretty straight forward.

Want to search on the city name first? You probably want your user to be able to do that too. After that you let them pick their product category and specific product. The resulting breadcrumb bar might be something like: CityName > Widgets > CityName.

The problem is pretty easy to detect: Widgets > Blue Widgets > CityName and CityName > Widgets > CityName have the exact same content. This makes them duplicate content. This is not a good thing. Let’s review some options for dealing with it:

1. One possible solution is simply to not offer both navigation paths. For many sites, this is pretty viable. Unless you offer a lot of very specialized content completely unrelated to your products that you are selling, you aren’t likely to rank for a city name anyway. Unless there is a compelling reason to offer both methods of navigation, just don’t do it.
2. You could also allow someone to pick their city first, and then when they pick a product, send them over to the other copy of the page. Basically, what you are doing here is sending someone from City > Widgets to Widgets > City. This is a pretty good solution for eliminating the duplicate content, but it can have a high usability cost. The nature of the cost is that your breadcrumb will be confusing to the user.The problem is that they selected a City first, and then a product, but the breadcrumb indicates the opposite. You can build the breadcrumb dynamically on the page, but from an SEO perspective, the breadcrumb bar is something that you want to use to reinforce the link hierarchy of your site.
3. Next up, you can offer the complete path, but NoFollow one path entirely. This provides a valid path for a user to follow, without any of the search engine issues outlined above. This is a pretty good option for managing the link juice flow too. Now the search engine only sees one “City Blue Widgets” page, and more of your link juice flows to that one version of the page.I don’t see any major down side to this option.

Related to all this is the issue of developing content. In what we have outlined above (hundreds of products and hundreds of cities) you are likely to have tens of thousands of pages. How are you going to get content for all those pages?

While that’s not today’s topic, knowing the answer to that is important in tackling these types of hierarchy questions. You are not doing anyone, including yourself, any good by publishing thousands of low content pages. You just up end up with loads of pages in the supplemental index of Google and provide lots of low quality signals to all the search engines.

You would be better off having a smaller site where the pages are all of high quality, and then grow the site over time as you develop more content. Even in this scenario though, it’s a good idea to know what direction you are headed in with before you design your initial architecture.