I find it strange, and maybe someone can explain this to me.
Yesterday I had a reputation score of 3992. Today my reputation score is 3302.
I see no indication why this would have happened when I look at my reputation page.
There are four big cases where you can lose a lot of reputation at once:
The only other explanation I can think of is some kind of bug in the reputation code.
This is possible because of deleted posts.
Go to your profile. And check the "show removed posts" checkbox. You now see the effects of deleted posts.