[brudgers]

It means that:

1. You didn't say what you thought you said,

:or

2. You said what you thought you said but didn't say it in a way that everyone understood.

:or

3. You said what you thought you said and someone didn't think it was worth saying.

:or

4. You didn't say what you thought you said and some didn't think what you said was worth saying.

:or

5. Karmic forces were at work.

It's worth assuming that the ones over which you have control are the reasons for a downvote, since those are the only ones from which you can learn. And given that everything else evens out statistically over time, it's not as if downvotes will ever stray too far from constructive criticism.