At first glance, it's an ad like any other. The picture shows two pre-teen-age boys lounging beside a limousine, which is parked by the Dulles Airport departure gates. The boy in the foreground, who looks quite unhappy, is holding what looks to be a familiar credit card.

The text of the ad reads:

"You've run away from home. . . You're at the airport. You have no money to pay the limo or for the plane tickets. What will you do? What will you do?

"The America [sic] express card. Don't Run Away From Home Without It."

All in good un, thought Bill Regardie, editor of Regardie's Magazine, a local business and real estate semimonthly. When Regardie wrote the ad and placed it on page 10 of the July/August issue, he thought it would be obvious that it was a spoof on the well-known ads of American Express. Surely, no one would take the Regardie gag seriously.

Lawyers, it appears, take everything seriously.

"The day it came out, the calls starting coming from American Express," said Edward Weidnefeld, Regardie's attorney.

"The people at American Express pretty much had one message: "You'll hear from our lawyers." And indeed, Regardie's did."

The message: Undo the damage. The solution that was finally reached: Regardie's would publish a notice in "a prominent place" in its September/October issue. The notice would acknowledge that Regardie composed and published the ad without the knowledge of American Express. In return, American Express would agree not to sue for damages.

Count your blessings, gang. At least there's not going to be any prolonged litigation. But the Regardie's compromise begs the big question:

Why doesn't American Express have a sense of humor?

"We have a legal responsibility in cases like this to police our [trade]-mark," said James Zalewa, a Chicago attorney for American Express.

"The company goes to great lengths to advertise its products. So this sort of thing is cause for some concern.

Aw, come on, Jim. The guy was obviously kidding.And it just may be that an ad spoofing American Express attracts as much attention to the company as its own ads. What do you say to that line of reasoning?

"Nothing," Zalewa replied. "Mama didn't rise no fool."

What's this? A sense of humor? In a lawyer?

If only Zalewa's clients hadn't left home without theirs.

Herman C. Orling of Arlington is about to scratch himself bald trying to figure out the District government.

Herman is an accountant who used to have an office at 1625 I St. NW. Recently, the District government changed its rate of tax for professionals doing business in the city. Herman calculated that he was entitled to a refund. So last December, he filed for $79.45.

In July, he received a check for $3.31 -- an amount the District government didn't explain.

Worst of all: Herman received the check on July 7. It was dated April 1, 98 days earlier. And it bore the notation: "Void 90 Days From Date."

Biff Howard of Vienna was so taken with a recent item in this space about Metrobus transfers that he did a little research into other statistical curiosities that surround our buses.

"I discovered that if you took all 7,306 Metro employes, allowed for 5 1/2 feet apiece and staked them end to end, they'd reach from the Lincoln Memorial to Seat Pleasant.

"If you took the system's 1,560 buses and stacked them end to end, they'd reach from the Woodrow Wilson Bridge to Silver Spring.

"And if you took all the members of the Metro board and stacked them end to end, they'd all go off in different directions."

John Lawrence of Crofton says he isn't about the degeneration of reading skills in the last 10 years. "My 16-year-old punk rock nephew reads about as well as he did when he was six," John says.