The
Onfocus Tooltips extension
improves the behavior of title-attribute tooltips
so that they also work from element focus.
Use the Tab key or equivalent to move around this page and you'll see the script in action.
This extension is not supported in Win/IE5, Opera 7.0 or Safari. The script could work in Safari 1.2 or later, but isn't implemented because it doesn't support CSS2 System Colors - the tooltips would come out as white text on a white background.