http://www.soxiam.com/Code/DefinitiveCSSImageReplacementSolution

Finally! A text replacement method that works in all situations. It's not pretty, but it works! The idea is actually fairly simple... use content property for modern browsers and expression for IE, plus implement the old way for IE 5/Mac.

• It works in Opera, Firefox, Safari, IE 5/Mac, and IE.
• It is also completely semantic and accessible with Images off, CSS on.