Well a strange thing happened. Last night when I came home my web site was broken. I could not be bothered working out why, though a quick search indicated the line where the error occurred and there is a strange ip address in the log (220.127.116.111172998283). So I rolled the site back to the previous version. Very easy to do. Today when I went to my page, what I had done last night was undone, and one directory was recreated with nothing in it. (I had moved it else where as it was the candidate for what was wrong.) The site was working again as it was before I returned home yesterday. The change I made to roll it back was unmade. Very strange.