You can find information about the 404 Error page management and how it seems to be much better handled now.
Thanks to Aderson's video, I even think I can manage to make it work on my website.
But what about the old way to do things about the custom error pages specified on the "web.config" file ?
<customErrors mode="On" defaultRedirect="Error.aspx">
<error statusCode="404" redirect="Error404.aspx" />
</customErrors>
Am I good to go by just removing the 404 line, if I use the new 404 error managemment ?