I've added whats required in the web.config file
<customErrors mode="RemoteOnly" defaultRedirect=/DefaultError.aspx">
<error statusCode="404" redirect="FileNotFound.aspx" />
This works fine for whenever i try to type in a webpage with a .aspx extention that doesn't exist. However, if i just try to type in "mysite.com/stuff" then it doesn't seem to trigger the 404. Does anyone have an idea why? Thanks.