It's print advertising's tiny type, fit for reading by mice, or a speed-talked disclaimer on TV or radio that often makes an advertised claim false or misleading.
"FREE BOX OF CORN FLAKES . with purchase of a box at regular price."
Companies selling cable TV packages, cellphone service, restaurant food or just about any type of retail good or service might be guilty of it, said Edgar Dworsky, a former deputy attorney general in Massachusetts, who tracks such advertising fibs at MousePrint.org.
"Companies like to put the happiest face on their claims, but they know if they really told the truth in the big print, people would be less interested in the offer," said Dworsky, also founder and editor of ConsumerWorld.org.
Marketers think it's OK to say almost anything in an ad as long as they reveal the truth with an asterisk, Dworsky said. A fair-advertising rule would be simple: "The fine print can't change the meaning" of a primary claim, Dworsky said. "But unfortunately, I see advertising that does this every day."
Here are questions and answers about mouse print.
Q: Where am I likely to find mouse print?
A: It's all over the map, Dworsky said. "If they advertise, they probably have fine print. I can't say one industry does it more than another."
Recent examples include Best Buy's new policy to match online prices, which sounds great. Fine print reveals Best Buy will match prices of a few specified online retailers and only on certain categories of products. That will exclude some of the best sale days, such as Black Friday.
Others are T-Mobile's "unlimited nationwide 4G data" service, which comes with limitations; Excedrin pain reliever products marketed under three names but containing the same active ingredients; and an Avis offer for $30 off "your next Avis rental," which applies only to a weekly rental, fine print reveals.
The inside back cover of Consumer Reports magazine, in a section called "Selling It," is another great source of mouse-print revelations. Examples include the Tiki Island King Windfighter torch, which claims it "Stays Lit In The Wind." Yet, the fine print cautions, "do not use in windy conditions."
A box of Royal brand instant pudding shows the flavor in big letters as "pistachio" with a picture of nuts in the green dessert. The fine-print ingredients reveal the nuts are diced almonds, the flavor artificial and green color from yellow and blue dyes.
A TV ad for Western Sky Financial offered loans of up to $5,000. The small print says, "The APR for a typical loan of $5,000 is 116.73 percent with 84 monthly payments of $486.58." Notes Consumer Reports: "So if you take $5,000 and pay the loan back over seven years, you're out $35,872.29."
And be skeptical of sale prices. A 30 percent-off sale seems like a good deal, but you have to ask, "30 percent off of what?" Sometimes, it's off a full retail price the retailer never charges.
Q: What can I do to protect myself against mouse print?
A: Simple: Read the fine print and be skeptical of claims that seem too good to be true.
"The consumer just has to be watchful and understand that most broad claims are going to have some type of limitation, footnote or disclaimer," Dworsky said.
That's not always easy in electronic media. "You almost have to have a TV set with freeze-frame capability, so you can read the fine print when it goes by so quickly," he said.
Q: Does the government monitor false advertising?
A: Yes. But there are limits to how much the Federal Trade Commission or state attorney general offices can do.
The FTC has been clear that "advertisers cannot use fine print to contradict other statements in an ad or to clear up misimpressions the ad would otherwise leave," according to the FTC's Division of Advertising Practice.
It has used the example of an ad for a diet product that claims "Lose 10 pounds in one week without dieting," with a fine-print statement "Diet and exercise required." The mouse print "is insufficient to remedy the deceptive claim in the ad," the FTC advises in a guide for small businesses.
The agency tends to focus on ads that make claims about health and safety -- ABC-brand sunscreen reduces risk of skin cancer -- and ads that consumers would have trouble evaluating for themselves -- ABC gasoline reduces engine wear.
"There are so many misleading ads that use fine print that no government agency is going to be able to review all of them," Dworsky said. "You've got to be your own advertising watchdog."
Q: Are there other types of mouse print?
A: A cousin is downsizing, which is especially prominent in food items. A firm will keep the price of a product the same but change the number or ounces in the container, disclosed in small print.
Many brands have done it, but a recent one is Kellogg's Raisin Bran. The 15-ounce box now contains 13.7 ounces.
While the new and smaller volume of the product is typically identified on the label, Dworsky counts downsizing as deceptive.
"The problem with downsizing of products is it's done in a really sneaky way," he said.
"Manufacturers will tell you, 'We don't want to raise the price,' " Dworsky said. "But of course they're raising the price because the coffee is going to run out sooner or you're going to get fewer glasses of orange juice or fewer servings of ice cream."
The American Marketing Association advocates that members adhere to ethical norms, among which is "foster trust in the marketing system," according to the group's website. "This means striving for good faith and fair dealing . as well as avoiding deception in product design, pricing, communication and delivery of distribution."