http://www.rab.com/public/political/2016PoliticalHandbook.pdf
The FEC’s federal campaign regulations extend to paid internet advertising. Political advertising on the internet must be accompanied by a disclaimer similar to disclaimers required in print advertisements.
The regulations affect commercial website advertising sold by broadcasters, regardless whether it is sold in conjunction with the sale of broadcast time. The regulations apply to all forms of website advertising, such as banner advertisements, streaming video, pop-up advertisements, and directed search results.