The whole HTML validation exercise is questionable, but validating as XHTML is flat-out masochism. Only recommended for those that enjoy pain. Or programmers. I can’t always tell the difference.

If you don't have people that care about usability on your project, your project is doomed.

You can achieve a shallow local maximum with A/B testing - but you'll never win hearts and minds.

The whole HTML validation exercise is questionable, but validating as XHTML is flat-out masochism. Only recommended for those that enjoy pain. Or programmers. I can’t always tell the difference.

We have to stop optimizing for programmers and start optimizing for users.

In software, we rarely have meaningful requirements. Even if we do, the only measure of success that matters is whether our solution solves the customer's shifting idea of what their problem is.

Writing code? That's the easy part. Getting your application in the hands of users, and creating applications that people actually want to use - now that's the hard stuff.