Accessibility pattern 1: use buttons for Javascript actions, not images

The is the first in a series of what I'm terming accessibility patterns and anti-patterns - one per post (feel free to argue that it's an idiom!) Here is an example:

Bad

  <img onclick="displayURL()" title="Display URL" ../>

Good

  <input type="image" alt="Display page URL - popup window"
        onclick="displayURL()" src=".." title=".." />