The main question should be if you want the Web-Server (and its add-ons) or some other process do the processing you want. If the Web-Server can't or you don't want it to handle this processing, NSCA has decided on some standards to help you on your way, Common Gateway Interface, a way to call a program and return data to the Web-Server.
CGI calls are handled in a common way outside the Web-Server while ASP, mod_perl, PHP etc. are handled by the Web-Server and its add-ons in an un-common way.

/brother t0mas