Doing taxes...what "Tax code" should I use for Internet Marketing income on a Schedule C?

I'm hoping someone might know this since anyone here making money has to do taxes. I'm doing my taxes online right now, and I'm filling out a Schedule C for my marketing income (filing as a sole proprietor). This is for income generated as an affiliate.

I'm to the point where it asks what the "Principal Business" is, and what the corresponding "Tax Code" for the business is. Well, it's easy to classify the Principal Business as "Internet Marketing", but there is no tax code for that.

What would be the proper Tax Code to use to classify Internet Marketing on a schedule C?

I don't want to bother with an accountant because I'm doing it myself like I have for the past 17 years. That's the only question I have regarding doing my taxes, is how is Internet Marketing classified as far as tax codes go. Surely there is someone here who's making money, who has decided to do their taxes, and might be familiar with this.

Apparently the only options from the current tax code that are even close are:

Internet Publishing & Broadcasting
516110 Internet publishing & broadcasting

Internet Service Providers, Web Search Portals & Data Processing Services
518210 Data processing, hosting & related services
518111 Internet service providers
518112 Web search portals
519100 Other information services (including news syndicates, libraries, & online information services)

Unclassified 999999 Unclassified establishments (unable to classify)

At this point I think I'm going to go with code 999999 and just classify the principal business as "Internet/Affiliate Marketing".

Has anyone done their taxes yet who knows this for sure?