The Web is a page-by-page medium. The backward and forward buttons on your browser's toolbar direct the browser from page to page. When Macromedia's Flash became all of the rage, developers and users started to see how Rich Internet Applications (RIAs) break this metaphor. You might click around a few sites, land on a Flash-based Web site, then click around in it for a few minutes. One click of the Back button and the ride is over. Rather than going one step backward within the Flash site, you completely lose your place.