<?php include('http://www.temp1.hangnailproductions.com/includes/nav.html'); ?>
You don't actually need to include your file via HTTP ,which is not equivalent of including the path at the server side.
Originally Posted by http://php.net/function.include
If you want to use the absolute path at the server side, use it like
(just echo the above serve variable to know what's your absolute file path to your roo directory at server side)
I usually define a constant like
at the top(or in config file, which would get included in all other files), to make it easier for typing the absolute path, like