September is national coupon month, which is great in theory until to try to use some coupons you found on the Internet and the store rejects them.

These days, it's hard to know if a coupon is valid or not.

Take for example new coupon for TGIFriday's advertizing a free dinner. The only problem is that they are counterfeit.

A real Friday's coupon is buy one entrée, get one free.

What's the difference? The first ones were too good to be true, just like other bogus coupons for free olive oil and one for $4 off Quaker Oatmeal.

You can usually avoid the bogus ones if you stick with official coupon Web sites and mommy blogs.

The Coupon Information Center says warning signs of a phony coupon include no expiration date, it offers free products or meals or the logo appears copied, shrunk or doctored.

Another warning sign: the coupons were e-mailed to you. Most legitimate grocery coupons cannot be e-mailed and printed.