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.
One of extra benefits is that it will function even within browsers that doesn't support, and/or clients that have disabled javascript engine to.
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.