I think this may be one of the most enduring topics I’ve dealt with, and it surfaced again a few days ago in a meeting:
Will the use of Flash and/or AJAX help or hinder the SEO of my site?

It’s a good topic as understanding it requires getting to the nuts and bolts of what is and what isn’t crawlable. The first thing to say is that I am coming at this from the position of a website owner, not a developer.

Decent developers may well know how to mod their Flash to make it friendlier for search, but many site owners and webmasters do not. Related to this is the fact that many people commission Flash work separately for their site, in the same way that artwork is commissioned- so they’ll not have access to the resources to tweak it.

With AJAX the situation is slightly different; it tends to be an integral part of a site. Entire pages may be in AJAX, or just some page components. When sites are built with AJAX there are methods to increase its search friendliness, but again these are often out-of-reach of most site owners (and, some may say, still not very effective). Theoretically having *some* AJAX components in a page will not harm SEO, but entire pages or sites will be a problem.

The main issue then is one of technical ability and full code access (to the site). In most cases that we have come across site owners and managers do not have these luxuries. In fact many people simply do not want to get involved at this level- but they are considering running Flash or AJAX, or both.

For us, the easy advice would be to say “just don’t do it”, but that kind of misses the point. Flash can add some much needed texture to a site, and AJAX can enable some really great functionality. Far better advice is to say “yes, do use it, but only where it will add value to the user”.

If you’re looking at a site refresh or a scratch build then AJAX and Flash should be considered, where are they are going to add value. Areas where they will likely cause problems are navigation, on-page content, site linking, and forms.

For further reading there is a great post on the AJAX issue by Maria Nikishyna.