root folder problem

I'm using a free shared server (to do some live testing)

I have most php pages in the normal root folder of my server, all works fine.
from a file within this root folder, using a php include to a file in a upper level folder is fine, but when I take users INTO a upper level folder and use files in there, includes to lower level folders wont work?

i.e.

server folder layout:

/www/
folders in www folder are:
/css
/images
/members

files in www folder are:
index.php
contact.php
(etc)

index.php calls the files from images and css fine (/images/imagename.jpg)
but
when the user logs in and is then using the files in /members

require_once('/footer.php'); does not work?
if footer is copied to /members folder, and the code changed to...
require_once('footer.php'); it works fine

so how, on a shared server do I tell it to go to the correct folder to use a file?

I also tried the full http://www.freeserver.com/footer.php
same problem