As mentioned in Hour 1, not all scripts are located within <script> tags. You can also use scripts as event handlers. While this might sound like a complex programming term, it actually means exactly what it says: Event handlers are scripts that handle events.
In real life, an event is something that happens to you. For example, the things you write on your calendar are events: "Dentist appointment" or "Fred's Birthday." You also encounter unscheduled events in your life: for example, a traffic ticket, an IRS audit, or an unexpected visit from relatives.
Whether events are scheduled or unscheduled, you probably have normal ways of handling them. Your event handlers might include things like When Fred's birthday arrives, send him a present or When relatives visit unexpectedly, turn out the lights and pretend nobody's home.
Event handlers are associated with particular browser objects, and you specify the event handler in the tag that defines the object. For example, images and text links have an event, onMouseOver, that happens when the mouse pointer moves over the object. Here is a typical HTML image tag with an event handler:
<img SRC="button.gif" onMouseOver="highlight();">
You'll learn more about event handlers in Hour 10, "Responding to Events."