We are taking some friends to Italy for a couple of weeks and they wish to see the larger churches in Florence and Milan, as well as the Vatican. Every website says something different about what the dress code is for men and women! The last one I read said nothing above the knee and shoulders must be covered. Is this correct?

yes

yes, that's correct.
No sleeveless, no shorts,no bare midriffs, no minis.

wait!

reverse that

everything above the knee must be covered
shoulders must be covered

Hi ashlash, I think the last part of your question was a mistype, it happens to all of us.

Shoulders and knees must be covered. Also your torso. Wear at least a short sleeve top and skirt or pants that covers your knees. Do not wear a top that leaves you midriff exposed between your top and the start of your skirt (or pants). Wishing you a beautiful time in Italy.

No low cut shirts/dresses for women and don't risk shorts that come to the knee. At the Vatican especially the "no shorts" rule is strictly enforced, no matter how long they are.

Be aware that although these rules are appropriate for all churches in Italy (and I would think anywhere else) in most places this is what is expected. And you may be chided by the locals if you are improperly dressed.

However, at the Vatican the rules are officially enforced - the guards will defiitely turn you away if you are too bare (legs above the knees, upper arms, a lot of bosom or any midriff exposed.)

topping

My mother was sitting on the steps of St Peters while I went to look at something else and saw several men turned away in fairly long shorts. They don't seem to like shorts at all on men.

Correct. It is a repectful thing and it gives Americans a bad name when they try to push in dressed inappropriately for the local custom. Carry a sweater or buy a large scarf while you are there if you must go sleeveless.
I never saw any one but American tourists wearing shorts.

in 1970, my sister was about to go into St. Marks in Venice when she was yanked out by a guard at the entrance. Her shoulders were bare. I got a great picture of the guard, the sign in English stating the rules, and a woman in jeans going into the cathedral.

A few days later, we took a tour that went to St. Peters. She wore here only dress that covered the shoulders. I suggested that she walk into St. Peters between the two nuns on the tour. She didn't and was pulled out for having a dress that was just above the knees!

While waiting for me to come out after the tour, she was reunited by a girl we had met a couple of weeks before in Salzburg. That girl and her friend were also denied entrance for short skirts. They even ripped out the skirts' hem to lengthen the skirts to no avail.

Later that summer there was a newspaper article about one of the entrance nun guards suffering from exhaustion from preventing all the improperly dressed from entering!