PHP include randomly not working

[ModernRevolutions]

Okay, i use a header, footer, style and index page set up, so every page i make has a PHP include. However, for some stupid reason its not working out of nowhere, I didn't even touch the code at all. it was this:

<?php include("http://www.modernrevolutions.vivid-avenue.net/layout/header2.php"); ?>

And i just changed it to:

<?php include 'http://www.modernrevolutions.vivid-avenue.net/layout/header2.php'; ?>

Which is what i found on a site. However, its still not working what so ever. Here is a link to my page:
http://www.modernrevolutions.vivid-avenue.net

[bluewalrus]

I think you need to contact your host

URL file-access is disabled in the server configuration...

[fileserverdirect]

Just use relative links:
include "layout/header2.php";
Be sure your include path is set to your site root!