When it comes down to it, are morals and ethics just personal preferences?

Are morals and ethics just personal preferences, or do they have something universal about them?

Example: Is “not killing other people” a universal rule, or is it just a preference that the majority of people tend to have, with a few outliers in the minority?

But don’t just think about killing to answer this question, think about any morals or ethics that you believe in. Why do you believe it? Do other people tend to agree or disagree with you? Does it seem universal, or just preferential to you (and/or others)?

(I tried to explain this as best I could. Please ask for clarifications if it was confusing :-D )