does nyone know how to set an error message to apply for a whole site? eg if someone typed in a non-existent page directory instead of getting 'page not found' they get the sites own page not found error page... ive seen it done on other sites but i cant work out how its done!
Depends on your server configuration, but they usually referred to as Custom error pages, or Custom 404s (although you can get more than just a 404 error). Talking to your hoster to find out if it can be done.