This code enables you to publish a CSS only with mouse click and keyboard tab image swap.
Attached is a Demo example of how it would look on IE6.
To ensure the greatest possible cross-browser compatibility/support this code uses CSS level 1 capabilities only.
Big images are asynchronous keeping the page as light and as fast as possible. The code itself will fall under 6KB if relative URLs are used. [here I'm using absolute paths to some real images available on the net for demonstration purposes only].
It's a copy-paste ready for preview demo.
It is HTML4.01 Strict and CSS2.1 validated.