<html><head><script>function lighton() { document.getElementById('myimage').src = "bulbon.gif";}function lightoff() { document.getElementById('myimage').src = "bulboff.gif";}</script></head><body><img id="myimage" onmousedown="lighton()" onmouseup="lightoff()" src="bulboff.gif" width="100" height="180" /><p>点击鼠标并按住不放！</p></body></html>