It might surprise you to learn that the most important button on your Web pages is not a button that you built into the page at all - it's the "Back" button built into the Web browser your customers all use. If you don't believe me, just watch yourself. Make a quick note every time you go to hit the back button (or use Alt-left arrow, or the like). I'm not talking about when you click on a link on the page that says "back" or "back to top" but just that simple button built into the browser chrome.

• The Back Button - How People Use Web Sites