This one could slip by you if you don't read your credit card agreements and statements carefully, and who does? Credit card companies are getting tougher on customers who make late payments. According to Liz Davidson, Founder and CEO of San Francisco-based Financial Finesse, if your payment is late, even by a day, you may not just get dinged with a late fee. Some creditors will also increase the rate you pay on your unpaid balances. These penalty APRs, as they're called, can be as much as 7% to 10% higher than the usual annual percentage rate. You could be punished for just a few billing cycles, or you may get stuck with the higher rate from then on. Credit card payers,