Safari spontaneously deleted all of my cookies. This morning when I was visiting my regular web sites, I noticed that I had to log in to all of them again. When I opened my list of cookies, I saw that it was very short and only included cookies for web sites that I had visited this morning. I normally have a very long list of cookies. I was able to restore my old cookies from yesterday's backup. I don't recall this issue happening before, and I don't know what caused it. Sorry I don't have any more information, but it just seemed to happen for no reason. I didn't do anything unusual today. There's nothing unusual in the console log, and no messages from Safari, to indicate what the problem would be.