Come the time that you decide that you are going to commit to a blog (a serious step forwards in your SEO strategy), the first step is to choose a domain name for it.
Options might include (for example):
Using a subdomain name of the blogging tool provider (in this example blogger.com).
A special subdomain set aside for your blog and possibly hosted on your own site or using a custom subdomain on a hosted site, such as Blogger.
A subdirectory of your own site, probably using a full custom blog solution such as WordPress.
Blogger (the blogging solution provided by Google) have just recently closed off option 3 when using their service, causing many people (us included) much work in switching to option 2.
So, which format of blog domain is best? Well, instead, we should perhaps ask which is worst? And that falls to option 1. Any SEO credibility that you build for such a blog will mostly funnel to the hosting domain – in this case blogger.com. If you link heavily to your own site from your blog then from an SEO perspective you will be able to drive some of that credibility to your own website, but frankly you’re wasting your time with this option.
From a pure SEO point of view option 3 funnels the most credibility gained by your blog to your own website, as Google, and the other search engines, just them all being part of one domain. This is the option that we had opted for with our blog originally.
Option 2 doesn’t funnel all the credibility gained by your blog to your website, as Google only loosely associates blog.websanity.co.uk and www.websanity.co.uk (an issue related to another important SEO concept called url canonicalisation). However, there is a far more important reason to recommend it than pure SEO alone, and that is, if your blog starts to gain credibility, then would you rather your blog appear in the search results, or your website? Or potentially both? Option 2 allows both your ‘commercially oriented’ website and your ‘information oriented’ blog to both appear in the results giving the best of both worlds – addressing the needs of people making both searches for services/products and for information.
So, in short, most of the time we would actually recommend option 2 – it might not be optimal from a pure SEO perspective, but from a point of view of gaining maximum exposure, I feel that it is often the best choice.