<!DOCTYPE html>
<html>
<head>
<script>
function lighton() {
  document.getElementById('myimage').src = "/bublon.png";
}
function lightoff() {
  document.getElementById('myimage').src = "/bulboff.png";
}
</script>
</head>

<body>

<img id="myimage" onmousedown="lighton()" onmouseup="lightoff()" src="/bulboff.png" width="250" height="350" />

<p>Click mouse and hold down!</p>

</body>
</html>