I have to give credit to Nikhil Kothari. He just ran a session the way that I like to see sessions run. As I read the title and abstract for the session, I was expecting not much in the way of new information. I actually attended the session mostly because it was the only one in this time slot that might be of interest.
Nikhil started out with just some basic stuff on AJAX. But very quickly he got past that and the session became very interesting. The idea is that if you plan on using AJAX in a "real" application, there are a number of issues that need to be address. Simple issues to identify, but complex to deal with. For example:
History
Say you have a page that makes a number of AJAX calls, updating the screen each time. Then you click on the back button. The typical action is to go to the page prior to the initial view of the current page. But what you generally what to do is go to the results from the previous AJAX call.
The solution is to use an AJAX UpdateHistory control. More details can be found on Nikhil's weblog here. It requires some work by the developer to determine when the browser history needs to be updated, but if you put the effort in, your users will love you. OK, not really. This is one of those features that users will ignore if it's there, because your site is working as they think it should. But if you don't have it, they will hate you. It's almost the same thing.
Indexability
If you have a page that uses AJAX to retrieve and display information, you have a problem with making that page appear in the appropriate place within Google. After all, Google depends on static data for its indexing.
The pattern that Nikhil is suggesting is to create a static page that contains all of the data. Make the data static on page. Put the data into a hidden div. Then create a separate frame and use script to pull the data from the hidden div into the frame. When viewed normally, the data will appear in the frame. When crawled by a spider, the script is not executed, so the data is just available for indexing. This pattern might not work in all situations, but there are enough to make it worthwhile being aware of. Again, a blog post (here) provides some additional details.
Overall, a nice presentation with some useful takeaways.