The ideal age range varies depending on the age of the participants. Obviously, a 10 year variance for a 13-year-old would cause more problems than a 10 year variance for a 50-year-old. I'm sensing that you might be asking how young you can date and have it still seen as acceptable. It really doesn't matter what others think. What matters is the relationship you have. If both of you have a similar maturity, it can work. If she can't relate to your generation, or vice versa, then don't expect it to last. If you are interested in older women, then, at your age, the sky is the limit.
Usually for men, in my opinion is always negative five years to his actual age in terms of maturity. So any men that is around my age is still not 'stable' enough for me, that is why I prefer the man to be much older than I. Men who are unstable in work or financial and emotional will have hard time to enjoy a lasting and meaningful relationship or even loyal to a partner. Better if he passed his mid life crisis and is very stable financially and career wise, so that he has more time for me. Look at Michael Douglas and Catherine Zeta Jones. Unless the man is much younger with super rich woman like Ashton Kutcher and Demi Moore. In my case an ordinary and average Jane is hardly to look for average Joe and to take age range as indicator for dating or relationship.
Currently, no more than 10 yrs older and no more than 6 years younger than my age
5 years younger to 9 years older
Plus/Minus 50% of my age, but always at least 18. :)
For me, I have difficulty thinking of being involved with younger men. Previously, I liked men who were a lot older than I, but as my age has increased, I would be dating men in their 70´s and above and I don´t want to be a nursemaid. Right now men my age and above are fine.