Gmail used a novel way to deal with an error situation that I’d like to point out. It won’t work in all situations, but in their case, when a heavy load on the server was the cause of the error, it was very useful.
They made the error page refresh (every 30 seconds I believe), so when the server was not responding, I didn’t have to do retry manually until it succeeded. Now, there is the possibility of causing a heavy load if everyone’s browser is refreshing every 30 seconds, but of the load-related error pages I see, the message is almost always to please try again, so all this is doing is automating what people are asked to do by the error page.
It also means that a user may not even realize there was ever an outage. The page could get an error, but then a few minutes later refresh back to a working page and the user will never know there was a problem.
It’s cool to see innovation being done in areas where the general impression is that it’s all been done before.