Great! Then I suggest you ask the question in the appropriate server-side coding forum. If you're new to it, then I suggest PHP. PHP works by interspersing PHP tags with your HTML tags. When a user browses to a PHP page, the server first interprets the PHP.

So to generate an alternate image, you might have something that looks like:


The trick, then, is to write PHP code that changes the value of the $myVariableImage string. So, armed with that little bit of foreknowledge, I suggest you go to the PHP forum and ask some questions there.