Tutorial “Go Back” Button
by Unknown in javascript , Tutorial 0
Browsers already have "back" buttons, so you'd better have a darn good reason for needing to put one on your page!
Input button with inline JavaScript
<input type="button" value="Go Back From Whence You Came!" />This is totally obtrusive, but you could fix that by only appending this button through JavaScript.
PHP
If JavaScript isn't a possibility, you could use the HTTP_REFERER, sanitize it, and echo it out via PHP.
<?php
$url = htmlspecialchars($_SERVER['HTTP_REFERER']);
echo "<a href='$url'>back</a>";
?>