Accessible tooltips using various ARIA attributes and some CSS trickery.
I initially wrote this to toggle visibility of the tooltips using JavaScript but then refactored to achieve this with CSS upon finding the following source: http://heydonworks.com/practical_aria_examples/
This method uses what is known as an Adjacent Sibling Selector in CSS: http://reference.sitepoint.com/css/adjacentsiblingselector
This example utilizes this method on form fields, a link element, and a simulated icon/button.