Developing an SEO-Friendly Website : Root Domains, Subdomains, and Microsites (part 1)

As search engines scour the Web, they identify four kinds of web structures on which to place metrics:

Individual pages/URLs

These are the most basic elements of the Web—filenames, much like those that have been found on computers for decades, which indicate unique documents. Search engines assign query-independent scores—most famously, Google’s PageRank—to URLs and judge them in their ranking algorithms. A typical URL might look something like http://www.yourdomain.com/page.html.

Subfolders

The folder structures that websites use can also inherit or be assigned metrics by search engines (though there’s very little information to suggest that they are used one way or another). Luckily, they are an easy structure to understand. In the URL http://www.yourdomain.com/blog/post17.html, “/blog/” is the subfolder and “post17.html” is the name of the file in that subfolder. Engines may identify common features of documents in a given subfolder and assign metrics to these (such as how frequently the content changes, how important these documents are in general, or how unique the content is that exists in these subfolders).

Subdomains/fully qualified domains (FQDs)/third-level domains

In the URL http://blog.yourdomain.com/page.html, three kinds of domain levels are present. The top-level domain (also called the TLD or domain extension) is “.com”, the second-level domain is “yourdomain”, and the third-level domain is “blog”. The third-level domain is sometimes referred to as a subdomain. Common web nomenclature does not typically apply the word subdomain when referring to www, although technically, this too is a subdomain. A fully qualified domain is the combination of the elements required to identify the location of the server where the content can be found (in this example, “blog.yourdomain.com”).

These structures can receive individual assignments of importance, trustworthiness, and value from the engines, independent of their second-level domains, particularly on hosted publishing platforms such as WordPress, Blogspot, Wetpaint, and so on.

Complete root domains/host domain/pay-level domains (PLDs)/second-level domains

The domain name you need to register and pay for, and the one you point DNS settings toward, is the second-level domain (though it is commonly improperly called the “top-level” domain). In the URL http://www.yourdomain.com/page.html, “yourdomain.com” is the second-level domain. Other naming conventions may refer to this as the “root” or “pay-level” domain.

Figure 1 shows some examples.

1. When to Use a Subfolder

If a subfolder will work it is the best choice 99.9% of the time. Keeping content on a single root domain and single subdomain (e.g., http://www.yourdomain.com) gives the maximum SEO benefits, as engines will maintain all of the positive metrics the site earns around links, authority, and trust, and will apply these to every page on the site.

Subfolders have all the flexibility of subdomains (the content can, if necessary, be hosted on a unique server or completely unique IP address through post-firewall load balancing) and none of the drawbacks. Subfolder content will contribute directly to how search engines (and users, for that matter) view the domain as a whole. Subfolders can be registered with the major search engine tools and geotargeted individually to specific countries and languages as well.

Although subdomains are a popular choice for hosting content, they are not recommended if SEO is a primary concern. Subdomains may inherit the ranking benefits and positive metrics of the root domain they are hosted underneath, but they do not always do so (and thus, content can underperform in these scenarios).

2. When to Use a Subdomain

If your marketing team decides to promote a URL that is completely unique in content or purpose and would like to use a catchy subdomain to do it, using a subdomain can be practical. Sites such as Maps.google.com and Blog.searchenginewatch.com are examples of where the marketing considerations make a subdomain an acceptable choice. One good reason to use a subdomain is in a situation where using a subdomain can look more authoritative to users as a result of creating separation from the main domain.

Be wary of press and media attention to the domains, as unsavvy users often don’t understand the concept of subdomains or that domains can be on the “World Wide Web” without a “www.” It is much less expensive to use a subfolder and have slightly less marketing panache than it is to educate through branding and advertising.

Subdomains may also be a reasonable choice if keyword usage in the domain name is of critical importance. It appears that search engines do weight keyword usage in the URL, and have slightly higher benefits for exact matches in the subdomain (or third-level domain name) than subfolders.

3. When to Use a Separate Root Domain

If you have a single, primary site that has earned links, built content, and attracted brand attention and awareness, it is very rarely advisable to place any new content on a completely separate domain. There are rare occasions when this can make sense, and we’ll walk through these, as well as explain how singular sites benefit from collecting all of their content in one root domain location.

Splitting similar or relevant content from your organization onto multiple domains can be likened to a store taking American Express Gold cards and rejecting American Express Corporate or American Express Blue—it is overly segmented and dangerous for the consumer mindset. If you can serve web content from a singular domain, that domain will earn branding among the minds of your visitors, references from them, links from other sites, and bookmarks from your regular customers. Switching to a new domain forces you to rebrand and to earn all of these positive metrics all over again.