We are looking for some tips over a performance and search engine optimisation (SEO) technique.
For our clients, we would like to place all of their page images in a sub domain in order to have a better browser related performance.
For example by replacing:
<img src=”/images/foobar.jpg” />
By
<img src=”http://images.domain.com/foobar.jpg” />
As stated, it seems like a good idea for performance, but our concern is :
How does this strategy performs in the SEO domain?
Thanks!
PS : Just some quick links …
Many sub-domain strategies: http://www.askapache.com/htaccess/apache-speed-subdomains.html
Only thing found stating against this use : http://econsultancy.com/blog/3559-50-seo-tips-for-online-retailers
Other interesting discussion on the topic, but not related toward images in sub-domain but microsites in sub-domains:
http://www.seomoz.org/blog/understanding-root-domains-subdomains-vs-subfolders-microsites http://www.searchenginejournal.com/subdomains-or-subfolders-which-are-better-for-seo/6849/
If you're just using the subdomain to source images, there's really nothing you should be worrying about. It's not as though you're trying to rank images for keywords, but rather the pages those images happen to be on.
Maybe a good anecdote to explain why this is orthagonal to SEO is the fact that you can, for instance, source a link to the jQuery API on your page from Google Code without expecting any loss of PageRank. In fact, Google hosts that API in order to make it faster. If you're doing something to simply optimize the loading of objects within the DOM structure, then there's little to worry about as far as search optimization goes.
You're much better off worrying about H1, H2, title, meta description, meta keywords, and having really useful content that include the keywords you're trying to optimize for. Other than that, keyword-directed links to the page both externally and internally can help. The impact of most other things is fairly debatable.