Be careful out there today. It is April Fools' Day.

April 1 is party time for folks with overactive imaginations. But it can be a disaster for the more trusting and gullible among us.

According to the Museum of Hoaxes, references to what was known as All Fools' Day first appeared in Europe during the late Middle Ages. Despite examinations of many early spring celebrations and festivals dedicated to trickery and mayhem, the exact origins of April Fools' Day remains unknown.

That uncertainly, in fact, gave rise to one of the Top 100 April Fools' Day hoaxes. In 1983, the Associated Press reported that a Boston University professor had finally solved the mystery. The prof, the wire service said, discovered that the celebration began during the Roman Empire when a court jester had boasted to Emperor Constantine that the fools and jesters of the court could rule the kingdom better than the Emperor could.

In response, Constantine decreed that the court fools would be given a chance to prove this boast, and he set aside one day of the year upon which a fool would rule the kingdom. The first year, a jester named Kugel was appointed ruler and he immediately decreed that only the absurd would be allowed in the kingdom on that day.

The AP story was picked up by news outlets nationwide. Just one problem. The quoted professor lied.

That prank ranks 73rd on the top 100 hoax list. There are several others that are just as silly, such as the invention of Smellovision (51), the Sydney iceberg (17) and one of my all-time favorites, the tale of baseball's Sidd Finch (2).

Tax teases: A tax-related hoax, the fake Hawaiian federal refund, comes in at 38.

Back in 1959, as Hawaii was officially becoming our 50th state, a Hawaiian radio station announced that Congress had passed legislation refunding all federal income taxes that the Pacific Islanders had paid during the previous year. Thousands of people believed the report and most didn't take the announcement that it was all a joke very well.

More recently, and not restricted to April 1, word of an e-mail tax made the rounds. It didn't make the top 100, but it did get folks worked up when it first appeared in the late 1990s and early 2000s. That's when e-mail boxes were full of messages warning that Congress was about to impose a 5-cent fee on each piece of e-mail in order to make up lost U.S. Postal Service revenue.

The alert even appeared in other countries, tailored of course to those locales' snail mail delivery systems. And while a small tax on spam would indeed make up many budget shortfalls, the report was fake.

Tax season scams are no joke: April Fools' Day arrives during the peak of the annual tax-filing season, so it's appropriate that we remind folks of the myriad tax schemes out there.

This year's Dirty Dozen Tax Scams range from the perennial identity theft phishing attempts to fake charitable deductions to frivolous tax arguments, which themselves are detailed separately here.

There also are Web sites that, at least in name, seem like the real IRS deal but, says one Congressman, could be trying to lure unsuspecting filers into thinking that advice and offers on those faux IRS sites are government sanctioned.

So during this time when taxes and tricksters often team up, be alert and a bit skeptical. If you fall for a tax hoax, the joke will be on you and it's not a laughing matter.