We'll onmouseover fading then onclicking gets a bit more complex and you'll probably have to look at a jQuery solution. Below is a simple example, just change 'yourImage.jpg' to the name of your image. You can then add an onclick event to the image using the built in Dreamweaver behaviours
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Untitled Document</title>
<script type='text/javascript' src='https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js'></script>
<script type="text/javascript">
$(document).ready(function(){
$(".fade").hover(function() {
$(this).stop().animate({opacity: "0.2"}, 'slow');
},
function() {
$(this).stop().animate({opacity: "1"}, 'slow');
});
});
</script>
</head>
<body>
<img src="yourImage.jpg" class="fade" width="200" height="150" />
</body>
</html>
