Can somebody explain revolts to me?

[Waldin]

I had a small but perfectly happy city on the borders of my empire, and suddenly they revolted and the city went over to the neighboring empire. Is that related to culture? What can I do to avoid it?

[notyoueither]

Don't settle cities on the outskirts of other civ borders.

Don't neglect culture for any of your cities.

[Bhruic]

Basically, you have to worry about "culture comparison". The culture of your city is "warring" against the culture of your neighbour.

The best way to win that battle is to increase the culture in your city. Build things like libraries, temples, etc, that increase your culture.

Bh

[Amniotic]

If you hover the mouse over your city, I think it gives you some sort of metric for how strong your culture is there. A percentage? I don't have the game around. It may be that you can do this on any tile, not just the city tiles.