The previous property is used to get the URL for the previous entry in the history list.
<html> <head> <title> Using the previous property of the History object</title> </head> <body> <script language="JavaScript"> <!-- netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead"); --> </script> <form name=form1> <input type="button" value="Get Previous" onClick='alert(window.history.previous)'> </form> </body> </html>