How can I turn off the + / - that shows up in my oscommerce product listing?

Oscommerce by default adds a + or a - next to the sorted column in your product listing.  Of course, for many people, this doesn't mean anything, and actually looks a little unprofessional.  Here's how to get rid of it:

edit the file:

includes/functions/general.php

Find this line:

$sort_suffix = (substr($sortby, 0, 1) == $colnum ? (substr($sortby, 1, 1) == 'a' ? '+' : '-') : '') . '</a>';

and modify (I usually comment the line out, and make a new line, so I can revert if necessary) it to look like this:

$sort_suffix = '</a>';

Save that file and you are done.