HTML and CSS Reference
Session history is an HTML5 add-on that extends the
simple, but the trick is knowing when and why you
should use it.
If you've never noticed the history object before, don't
be alarmed. Up until now, it's had very little to offer. In
fact, the traditional history object has just one property
and three basic methods. The property is length , and it
tells you how many entries are in the browser's History
list (the list of recently visited web pages that the browser
maintains as you skip from page to page across the Web).
Here's an example that uses it: