Well, I'm going to offer a fairly different opinion to some I've read....
I'm 26, and I am engaged to a 56 year old Divorcee. Now our circumstances are somewhat unique, as we first met, and fell for one another online through skype. I'm blind, and thus couldn't see his profile pic well enough, and I'm not the sort of girl who goes through the meaningless ASL chitchat, because I really don't care what age, location or sex you've got, I care about your intelligence and views, that is what I judge new friends on.
and he is intelligent and caring and a wonderful person to talk to, so we kept talking. I found myself getting up early or staying up late just so I could spend more time with him.
anyway, it got to the point where I needed to be honest with him about how I felt, otherwise, I didn't think my friendship was going to be entirely honest. I didn't know if he was married, had children, or anything, and I was setting myself up to be disappointed. it took me hours to get out what I wanted to say, and it turned out that he felt exactly the same, and we were so happy. Only then did it occur to me to ask how old he was.
that's when I found out. 55 at the time. Now, maybe, before I had feelings for him, I might have had an issue with it, and it never would have happened. but after it happened, those feelings are no less, I didn't stop loving him, it hardly even effected me. He's no less the man I fell for just because he's older than I thought he would be.
so now, my opinion is is that age, unless a question of legality is involved, is not so much a concern if you're both prepared to compremise, and if you both love one another enough that in your own hearts it doesn't matter. Love really does break down all barriors.