Lets say I have a site called newcars.com and I want to create pages for new fords, new hondas, new toyotas, and so on. Which would be easier to rank, a subdomain like honda.newcars.com or newcars.com/honda ?
newcars.com/honda All day, everyday. If you use subdomains you are essentially ranking each sub as a dif. site. If you use subdirectories, you have one site with many directories and can use the strength of the host domain to influence the rankings of those pages.
Ditto the call on going with the subfolder instead of a subdomain. Authority DOES transfer from the main domain to a subdomain just not as much as with a subfolder. (this is the reason why so many WEB 2.0 blogs work so well for link building even though they are on subdomains) You usually want to go with a subdomain if you want to pass authority but create a "semi" barrier between the main domain and the subdomain. Lets use your example. If you are targeting the term "New Cars" and work hard building content to the main site and a bunch of backlinks and start getting a top position for that keyword. Now you worked real hard to get that traffic and you want to add value so you decide to add a forum or social networking application like Dolphin to the mix to engage your people more and bring them back to the site. Do you add it as a subfolder or subdomain? Well, truth be told, your users can ASSASINATE your search engine rankings if you go with a subfolder! Why? Because when they blog about you and link back are they going to use the term "New Cars" as their anchor text? No! They'll use the term "Car Forum", "Car Community", or "Car Site". As these links will pile up far faster than you could ever hope to build links for the term "New Cars" the search engines start associating your site with the term "Car forum" more and more and not "New Cars". New Cars might have a traffic value of 6,000 uniques p/day and Car Forum only 600 uniques p/day. This is a big problem. That's why you would build the forum or community as a subdomain. It isolates it from the main domain, but authority can pass between them based on how you setup your internal link structure. But anyway...most of the time, you go with a subfolder.
Excellent, well thought out and explained answer! I was sort of looking for the answer myself and stumbled upon this post. Thanks for taking the time to thoroughly explain your answer rather than just posting an answer with just a couple of words. +REP Added!
Was wondering the same thing. Glad to hear the hassle of setting up sub's and then tracking them effectively isn't necessary.
I'm having a similar problem too. The Expert has shed some new light to me regarding keyword links working against your site. Say my website is divided into 2 sections, whilst they are slightly related, their content, marketing strategy and keywords are different. (I want to submit 2 urls individually into directories and search engines as they are of different content, titles, descriptions and keywords) Would having them on subfolders cause problems : 1) weakening my keywords for each url in search engines (if there's such a thing)? 2) rejection / penalty for submitting 2 urls from the same domain? Ultimately, the question is, can i have 2 different SEO marketing strategies on 2 urls (on sub folders) on the same domain? thanks : )
search engine consider sub domain as a new domain. You have to do full optimization for it to get into serp. But by using folder newcars.com/honda it is easy to get PR and appear in serp. I suggest: newcars.com/honda