Can you produce an HTTP 404 error on your wordpress blog on-demand? Try it. Chances are that if you have pretty permalinks enabled on your blog, wordpress will automatically match any URL begining with the URL-path you typed and redirect to an existing post instead of showing up a 404 error. For example http://www.advancedphotography.net/how redirects to http://www.advancedphotography.net/how-many-types-of-cameras-do-you-know/ (by the way AdvancedPhotography.Net is doin great;) ). Not bad. Except that the visitor is directed to an unintended page instead of being notified of the slip.
The 404 page is there for a purpose – and it should be used to notify the visitor about the page which could not be found. If your site can’t produce a 404 page then that’s bad for SEO too. Here’s a one-liner to fix this problem for you. Find your functions.php file in the current theme. Go to the Admin panel (Dashboard) > Design > Theme Editor > Seletct “Theme functions (functions.php)” at the far right to edit it. Add the following line right at the top after <?php
//kill cannonical redirects remove_filter('template_redirect', 'redirect_canonical');
This shall take care of the problem and will ensure that visitors get to the 404 page when an incorrect URL-path on your blog is accessed.