What is the correct IRS Business Activty Code for Sched C for internet affiliate marketing?

Does anyone know the correct IRS business activity code to use for a small business that makes money by marketing online (all pay per click search) for internet retailers and gets paid a commission for each referral that leads to a sale? (no inventory – just advertising and commissions based on sales referrals. All done online.)
Thanks!

518210 is the code for data processing, hosting and related services. 519100 is for other information services. I hope this is what you are looking for.

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