Choose an Accessible Image Replacement Method
http://www.456bereastreet.com/archive/200712/choose_an_accessible_image_replacement_method/

Johansson, Roger
456 Berea Street
2007

Abstract:

The technique of using CSS to replace normal HTML text, mostly for headings, with a background image in order to achieve a particular look has been talked about many, many times since early 2003.Several different image replacement methods have been proposed, each with their pros and cons. Some methods create accessibility problems, while others place restrictions on the type of image you can use or force you to use extraneous markup. No method that I am aware of is perfect.