Coupon Ethics

As I'm a pretty recent couponer (yes, it's a word), I'm trying to learn what the appropriate coupon ethics are. Here's an example from yesterday:

I had a coupon for $1 off 2 packs of Rayovac alkaline batteries. On various sites, I'd read that there were some Rayovac batteries on sale for $1 at Target. People using 2 coupons were getting them for free! Well I went to check it out (and buy 2 loafs of bread for .50 each at the grocery store next door!) and by the time I was in line, I realized the packs I had in my hand were not alkaline as the coupon insisted. Also, how were people getting them for free since the coupon said it could not be combined with any other coupons, and the limie was 1 per customer. I only had one coupon so I felt OK about that, and I also figured that if the batteries I had didn't align with the coupon's requirments, it wouldn't work.When I gave the coupon to the very friendly cashier, she had no problem scanning the coupon. It took the dollar off just like that!

So here is my question that I'm researching (and we all know that "research" done online is totally legit . . .): do coupons have bar codes on them that let the computer know how to apply the price reduction, in accordance with the coupons requirements? Or is it solely dependent on the cashier reading the coupon correctly?

I want to make sure I'm doing this all legally so I'd love to hear anyone's thoughts on the subject as well as any legitimate sites that provide coupon guidlines. Here is a great article I found and I'm now headed over to one of my favorite sites, The Coupon Mom.