Stefan Koopmanschap has shared some of his thoughts on something that a lot of sites could be doing better - making their sites fail gracefully.
Error pages. Most people don't really consider error pages when building a website or application. They usually contain some debug information so that when something goes wrong the developer knows what is wrong. But in a lot of cases when an application goes into production, this information is still exposed.
He points out a specific example of a recent time when the only thing thrown to the page was an error about a database connection rather than anything more informative or useful to the typical visitor. He recommends that, at the very least, a website should still present these errors in a template similar to the rest of the site.
Your average visitor will come to your site expecting information. If something goes wrong (which can always happen), they only need to know that something went wrong, and perhaps they should get a phone number or e-mailaddress where they can report the error.