JavaScript is commonly used to add functionality to HTML documents. There are two ways to do this, with level one event handlers or using unobtrusive JavaScript. One allows you only to assign one event handler to an event at a time and is deeply coupled to your HTML markup. The other allows you to assign as many event handlers to an event as you wish and completely removes JavaScript from your markup. Do you know which is which? This tutorial will cover what the difference is, why using unobtrusive JavaScript is a better approach and how to implement unobtrusive event handlers using the Prototype JavaScript library.