I have a custom "Error 404" page set up to catch any arbitrary URL that users enter for my site, and serve dynamic content related to the words they entered - eg, "www.mysite.com/banana" or "banana.mysite.com" would display information pertaining to the word "banana," without having a static page or specific .htaccess entry for it (as there are too many possibilities of what users might type). What I want to know is, will search engines know that this is an Error 404 page, and treat it differently (negatively)? The content will be genuine, and form a core part of my site, but I worry that if search engines are specifically aware of its 404 status then they might consider the page a useless result of a dead/broken link. Can anyone confirm or dispell this?