Hello. I am looking at the following tutorial:

<!DOCTYPE html>
function changeImage()
if (element.src.match("bulbon"))

<img id="myimage" onclick="changeImage()"
src="pic_bulboff.gif" width="100" height="180">

<p>Click the light bulb to turn on/off the light</p>


What I don't understand is this line:

Where does "myimage" come from? Is "myimage" the name of a file? Is "myimage" the name of an object that I have to define somewhere? I assume that "pic_bulboff.gif" is the name of a file that should be kept in the same directory as the web page.

However, I would think the tutorial would do a better job of explaining where all these things come from. Anyone know of a better tutorial?