The US Federal Trade Commission called Tuesday for potentially bedeviling fine print to be "clear and conspicuous" as ads follow people onto smartphone screens or online social networks.

The FTC updated its Dot Com Disclosures guidance advising advertisers how to avoid charges that digital ads are deceptive because information about conditions, risks, or costs gets short shrift for the sake of screen space.

"Advertisers should ensure that the disclosure is clear and conspicuous on all devices and platforms that consumers may use to view the ad," the FTC said in a release announcing the updated guidance.

"Advertisers using space-constrained ads, such as on some social media platforms, must still provide disclosures necessary to prevent an ad from being deceptive."

The FTC advised marketers to avoid making people click on hyperlinks to reach disclosures or relegating the information to automated 'pop-up' boxes, which are often blocked by Web browsing software.

The original Dot Com Disclosure guidelines were released in 2000, prior to the booming popularity of smartphones and tablet computers.