[JonM]

Okay, seeings how I assume this is a image link let's get down to buisness

the CSS code:

a {
  background: url("http://image.com/image/image.jpg");
  /*then the rest of course*/
} 
a:hover {
  background: url("http://image.com/image/otherimage.jpg");
}

Then of course

<a href="index.php">Home</a>

Now this is untested, and can't be used in certain cases. But this can easily be modified to work to your needs This is meant to get you on a start. For more indepth look at all this I'd recommend www.w3schools.com