404 auto-email php script - emails me when someone lands on the 404 page and what page they were looking for
Having users help report errors for you through a contact form is great, but only a small percentage of users are likely to do that. An alternative is to have your 404 page automatically report the error to you. There are many ways you could do this. A quick-and-dirty way to do it would be to make your 404 page a PHP file, and use the mail function to send an email of the URL that was landed on.
<?php mail("chriscoyier@gmail.com", "404 report", $_SERVER['REQUEST_URI'], "From: chriscoyier@gmail.com ") ?>
NOTE: The above code is probably fine for a small site but not very practical on high traffic sites. Writing the errors to a Database in those circumstances is probably more practical.