I would be very careful with that interface (actually I would never use it!). It's a very old posting and has errors (that are mentioned in it) and omissons (like no power wiring shown for the hex invertor chip) and requires a RS-232 comm port which many modern PCs don't provide anymore.
A serial interface based on a MAX232 type RS-232 to TTL convertor is much more commonly used these days, if you indeed have a RS-232 comm port on your PC. There are also plently of USB to TTL convertor cables or modules that make it very simple to add programming capablility to your standalone set-up, like this example:
http://store.fundamentallogic.com/ecom/index.php?main_page=product_info&cPath=6&products_id=31
Lefty