if($_SERVER['HTTP_HOST'] == 'blue.server.se')
{
header("Location: http://red.server.se")
}
You need to end your PHP line. It's creating an error, and PHP errors aren't configured to display.
You code should be:
if($_SERVER['HTTP_HOST'] == 'blue.server.se')
{
header("Location: http://red.server.se");
}
~Brett