Does Your 404 Page Return a ‘Not Found’ Response?
Author:
Ash 
Search Engine Optimisation, SEO
Adding to a post from earlier this year on 404 Error Pages For Usability and SEO, which looks at how to create a 404 page that is both user friendly and search engine friendly, I thought I’d look at the responses the server gives when viewing the 404 page.
Many 404 pages give a ’200 Found’ response, which is the same response that any other page that should be indexed gives. This isn’t quite what we’re after with the 404 page. First of all, it probably shouldn’t be indexed.
Some sites are set up so that no matter which non-existent page you visit the 404 page is displayed on the URL visited. For example, http://www.domain.co.uk/non-existent-page.html, http://www.domain.co.uk/not-a-page.html and http://www.domain.co.uk/i-dont-exist-either.html all display the exact same 404 page at any of the URLs visited, without redirecting.
If this page also returns a ’200 Found’ header response then each of these pages could potentially be indexed and could also cause issues with the search engines finding an infinite amount of duplicate content on your site.
So, what’s the alternative? Make sure that your 404 page actually returns a ’404 Not Found’ header response. If your site is running on a PHP server simply add the following to the very top of your 404 page source code, before any output is sent.
<?php
header("HTTP/1.0 404 Not Found");
?>
For example;
<?php
header("HTTP/1.0 404 Not Found");
?>
<html>
<head>
<title>Title Tag</title>
<meta name="descript...
Remember, if you are not using the .php file extension, you will need to edit your .htaccess file to allow it to parse PHP within your HTML files, which I’ll go through in another post.
You can find more information on the technicalities at http://php.net/manual/en/function.header.php
Finally, you can check your page header response at http://web-sniffer.net/, http://www.seoconsultants.com/tools/headers or download the Live HTTP Headers Firefox plugin.
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