Are printable coupons accepted at stores?

I hear alot about all these websites that have all different types of coupons, so I went to coupons.com and printed out a few and took them to a Food 4 Less grocery store and they wouldn't accept my coupons. I spoke to the Manager and he still said no, he said that they don't get paid back for those coupons. Is that true or was the Manager just being a JERK!!!