HARRISBURG -- WTF.

Three little letters. On a license plate. They didn't mean anything to 60-year-old Mary Ann Hardee, a North Carolina resident.

But then her tech-savvy grandchildren, who were LOL (Laughing Out Loud), clued her in: These days, the WTF on her license plate means "What The (expletive)" in text messages and online lingo.

"Once it was revealed to me, I developed this real self-consciousness," Mrs. Hardee told her local newspaper, the Raleigh News & Observer.

So she complained to her state Department of Motor Vehicles, which said SRY (sorry) and promised to issue a new plate. In late June, it made the same offer to nearly 10,000 others with WTF in their plates.

DYJHIWTH? (Don't You Just Hate It When That Happens?) It's been happening to transportation and motor vehicle departments all over the country. Pennsylvania's Department of Transportation says it has measures to prevent some of these embarrassments.

Earlier in the 21st century, PennDOT stopped issuing plates with a vowel between two letters, said Danielle Klinger, CRC (community relations coordinator) in the SAD (Safety Administration Department) of PennDOT. The department has also banned the letters I, O, U and Q from standard plates, since they can be confused with numbers.

"The primary purpose of a license plate configuration is to be able to identify a vehicle," said Ms. Klinger. The letters and numbers "are not intended to represent a particular meaning."

Ms. Klinger said that in 1999, a woman complained that the DAD in her license plate reminded her of her late father. Others have complained about the number 666, which some people believe is a demonic number.

Vanity license plates, which allow drivers to customize letters and numbers for an extra fee, are scrutinized and checked individually, Ms. Klinger said.

"We use a variety of resources in the vanity plate review process, including acronym and slang dictionaries, translation dictionaries and Internet resources," Ms. Klinger said.

She said the state has a list of about 9,600 alphanumeric configurations that it bans from plates. Most come from the Internet Acronym Directory at the Web site www.gaarde.org.

"The use of acronyms is not prevented under the vanity plate program," she said, but "at times, the department exercises its authority to refuse a combination of letters, numbers or both, where connotations are deemed offensive in nature," or OACB (offensive as can be).

Sometimes the offending letters keep popping up.

A week after the WTF episode in North Carolina, the Department of Motor Vehicles there realized it used the same vulgar acronym on its Web site, in an image of a sample license plate.

"I can't believe it," North Carolina DMV Commissioner Bill Gore said about the graphic. "Obviously, I didn't know [IDK] it was there."

According to the News & Observer, the flap over WTF came only a few weeks after Mr. Gore had to recall plates with the suggestive letters XXX, as in pornographic movies.