Banks are dangling their zero percent credit card offers for longer terms.

Conveniently, they're hitting just in time to pay hefty bills. But a closer look reveals there are some strings attached:

A "universal default rate." This means you're charged a whopping fee or interest rate -- as much as 26 percent or so -- if you're late or bounce a check not only on your credit card, but also on any of your other credit cards or loans. "A $35 [late fee] penalty is one thing. But if your interest rate goes from zero percent to 26 percent, that's about $700 or a little more than that!" warned Robert McKinley, chief executive officer of Cardweb.com, Frederick, Md. Efforts currently are under way in Congress to prohibit this practice.

A special fee or exorbitantly high interest rate on the remaining balance if you close out your account. About half the credit card issuers charge a fee or high double-digit rate on your remaining balance, McKinley estimates. "It's a no-win situation."

Even worse, card issuers today seem to know exactly how to snare you. Conveniently, as we sought a zero percent card to pay off our house tile, we first got a solicitation for zero percent interest for one year. Upon taking this offer, we got hit immediately with a change in terms. Irritated, we moved our outstanding balance to another zero percent card, which promised zero percent for an even longer period. Shortly afterward, we received yet another solicitation, promising zero percent interest for even longer!

That's when we pulled out the magnifying glass and looked at the fine print. What we saw was not pretty.

Although the solicitation's headlines promised zero percent interest through April 1, 2006, buried in footnotes "a" and "b" were these facts.

Interest rates are not guaranteed. They could go higher. Fixed rates could become variable rates or variable rates could become fixed rates. "We reserve the right to change the terms at any times for any reason," it stated.

Interest rates could zoom to a 25.74 percent variable rate if we: Are late with a minimum payment, exceed our credit line, are late paying another creditor or we bounce a check.

If we decided to close this account, the bank could demand immediate payment of our outstanding balance. If we fail to pay by the date specified, the interest rate on the remaining balance could soar as high as 25.74 percent!

All this in addition to a late fee that could run as high as $35. Also, if we are assessed any interest, it would be much more than with many other credit card calculations. This issuer uses the "two-cycle average daily balance method, including new purchases." Many other card issuers assess interest only over one interest rate billing period.

So what should you do if you get a zero percent or low-interest rate offer?

Always carefully read the box on the back of the solicitation that lists all fees and terms. Be certain to examine and inquire about any footnotes. Confused? Call customer service.

Monitor customer service response time. You don't need to be spending half of your life on hold.

Watch for universal default rates. In other words, does the issuer raise your interest rate or charge a fee if you're late with another credit card or loan payment? Are you charged if you bounce a check to a different credit card issuer?

Determine whether the attractive zero percent offer is guaranteed. Often, an issuer retains the right to charge a higher rate based on your credit history.

Watch for arbitration requirements. In the event of a dispute, it's best to retain the freedom of legal representation.

Examine penalties for closing your account. You always want the freedom to leave a bad deal for a better one.