Do you always have a default/index page?

Many times a website contains directories that don't have an index page, and this means a user navigating via the URL, see a 404 error. You don't want this to happen, so make sure you always have an index page in every directory, even if it's just to show the files inside it.

It is usually a default.aspx file, however depending on the webserver configuration; it might be index.html or index.php etc.