Thanks, MXM!

You mention an icon, but what is the icon? What purpose does it serve? It's not a button, or a link, or any other control. How would AT users perceive it? That would be disorienting to an AT user, not to mention that hovering is obviously mouse-user exclusive.

As for showing all the errors, you are right that it can be detrimental to show a lot of errors at once. However, that only becomes a problem if you have a lot of controls on the page. Form controls should be few per page, which means the number of possible errors will also be small.

Thanks!