As you probably know that Microsoft Internet Explorer 4+ supports expando properties on HTML elements. This means that IE remembers all properties on an HTML element although it doesn't know what to do with them. For example one might add an attribute called overSrc to an image element that can then be used in a custom script. A much lesser known feature is the expando methods. With this you can add methods to any html element. I'll show you a small (stupid) example.