2010 NAR Code of Ethics:
Article 12
Standard of Practice 12-10
REALTORS®’ obligation to present a true picture in their advertising and representations to the public includes the URLs and domain names they use, and prohibits REALTORS® from:
1) engaging in deceptive or unauthorized framing of real estate brokerage websites;
2) manipulating (e.g., presenting content developed by others) listing content in any way that produces a deceptive or misleading result; or
3) deceptively using metatags, keywords or other devices/methods to direct, drive, or divert Internet traffic, or to otherwise mislead consumers. (Adopted 1/07)
The rules may have changed since 2010.