I'd like to add:

* Don't roll your own standard controls

Seriously. Don't. You want a single-select box? Use a combo box or radio button group. Want an edit box? Use an edit box. Want a list that finds things as you type? That's in the standard too. Don't roll your own.

This "roll our own controls for everything" bothers me to no end as a screen reader user, because practically nobody properly follows ARIA best practices, and that leads to a less accessible internet.

Don't worry, they bother everyone else as well since they are usually broken one way or the other.