Alt text and title attribute

title
The "title" attribute is not a tool to convey accessibility. Most users, screenreader or not, never see title attributes.
 * Survey of results of assistive technology users testing title attribute access
 * A series of essays on "The title attribute - what is it good for?"

Except in form controls, title attributes are useless to 99% of users -- including sighted users, since most people don't hover long enough to see the tooltip.