When I spoke at SMX West in February on the “Unraveling URLs and Demystifying Domains” panel, I got pretty geeky with the regular expressions, rewrite rules, conditional redirects, and so on. I won’t geek out so much here in the post, so no I won’t be going into pattern matching gotchas that can make your regular expressions too “greedy” in your rewrite rules. If you want that, go download my PowerPoint. But here are some SEO tips relating to domains and URLs that don’t require you to wear (or own) a propeller hat:

• Subdomains and thin content microsites: Google’s treatment of subdomains as subdirectories really means that you shouldn’t treat subdomains as a means of creating tons of easy thin-content microsites. You won’t be able to lock up all the slots in the first page of results anymore with the subdomain tactic, as Google’s now viewing them as part of your main site. Yes, use subdomains for managing your website and doing load balancing. No, don’t use them purely for SEO reasons.
• Speaking of microsites…: Microsites can be very good and effective if they are built out with high quality in mind. The Microsite should not solely be redisplaying the very same content as the primary, main website. Use unique content and avoid duplicating text content between two sites. In this way, Microsites can be very beneficial in terms of demographic targeting, and focussed keyword targeting. Microsites are very bad if they are merely duplicating content with only slight cosmetic changes, like displaying a product description on a page with only the UI different – different header, sidebar, footer. Search engines mostly ignore UI navigation and graphic display for the purposes of detection of duplication — they focus on text.
• Keywords in URLs: In our experience, keywords in URLs are beneficial when optimizing for Google, regardless of whether they’re in filename/directory/subdirectory names versus variable values in query strings. But, in other search engines, I think it’s more important that the keyword be in filename/directory/subdirectory, and the closer the keywords are to the root domain name, apparently the more weight they will lend.
• Word separators in URLs: If you have multiple-word keyword phrases in your URLs, it’s recommended that you use dashes to separate them. Ex: “blue widgets” could be done as “blue-widgets” in a URL. This is preferred over underscores: “blue_widgets”. Bares spaces cannot be used in URLs, so some “white space” character needs to be used – either the + (plus sign) or the character encoding for a space %20. I’m not a fan of using the character encoded version, as it’s not quite as pretty: “blue%20widgets”.
• Other TLDs: If any sites are linking to the .org, .net, .info, .biz, etc., versions of your domain name, you’ll need to register those and 301 redirect them to your .com domain (assuming that’s the TLD you’re hosting on). However, if there aren’t people linking to those domains, and your domain doesn’t have fairly large amounts of brand name recognition, you may not need to bother with registering those. The majority of domain squatting occurs on .com domains in the form of variant spellings and typosquatting. For example, brandname.com may have people squatting on brand-name.com, brandnames.com, brndname.com, brandnme.com, brand-names.com, brand.names.com, etc.
• To www or not to www: Ideally you want one version of each URL in the search engine’s index – not one with a preceding www subdomain and one without. It’s best to 301 redirect all URLs to one canonical version that includes the www. You can accomplish this with an .htaccess directive. Here’s an example if you’re curious: RewriteCond %{HTTP_HOST} ^netconcepts.com$ [NC,OR] RewriteCond %{HTTP_HOST} netconcepts.co.nz$ [NC] RewriteRule ^(.*)$ http://www.netconcepts.com/$1 [R=301,QSA,L] (oops, did I promise not to get too geeky in this post? Sorry!)
• Domain age and trust: Google’s patent on “Information retrieval based on historical data” indicates that the age of your domain name could be used to determine how trustworthy your site might be. This is particularly important to know for those who have newer domain names. It’s recommended that you increase the registration period for your domain so the expiration date will be further in the future.
• Domain tasting: Some Webmasters have been known to do “domain tasting” — registering domains for just a couple of days to see what keyword traffic they get. However, Google recently announced that it’ll stop displaying AdSense ads on domain tasting sites as a way of fighting this practice.
• Cybersquatters: What do you do when someone’s cybersquatting on a domain name based off of your company’s trademarks? What about when you find your excellent content on a splog? I’d check with your legal department to see if you can grab the domain away from them and 301 redirect it back to your primary domain/URL. You can submit a DMCA takedown notice to the engines and to the offender’s web host. You might also consider contracting a firm like MarkMonitor to help you police your domains in an ongoing basis. MarkMonitor uses software to keep tabs on all domain registrations that include your key mark terms and variants, and it’s fairly effective.

Let me know if you’d like a geekier post on rewrite rules and the pattern matching / regular expression stuff.