PHP/HTML/HTTP REFERER
HTTP_REFERER and HTTP_USER_AGENT
<source lang="html4strict">
<?php
if (isset($_SERVER["HTTP_REFERER"])) { print "The page you were on previously was {$_SERVER["HTTP_REFERER"]}
"; } else { print "You didn"t click any links to get here
"; } ?> <a href="refer.php">Click me!</a> </source>