... base filesystem path. Pretty much everything I do, I include from base filesystem path so if I'm running the script from a different directory, I don't have to remember the relational path.
As for Tom_G's problem, its weird that the script giving the error is in the reg directory, but its asking for the file in the public_html directory. My thought would be that he is running the script from the public_html directory, including the main_dsp031701a.php file into that script, thus the path is public_html, but the hello.php resides in the reg directory, and thus can't find the hello file.
If you can't follow that (which I don't blame you), lets try a diagram....
public_html
|
|-executing_script.php
|
-reg
|-main_dsp031701a.php
-hello.html
(hope this looks right after being posted).
Anyway if the 'executing_script.php' was running and included 'main_dsp031701a.php', and 'main_dsp031701a.php' included 'hello.html', I could see the error happening.
The other reason again would be making sure the web server user (usually nobody) has read privelleges to the 'hello.html'.