This is the first google update since I have work SEO. I do not know how it goes and how the changes affect SERP. but I know that some of my sites were on the first page for main keyword and now, after update, some of them are not even in top 200. My question is: is it possible that the site which was at position 10, for one (after google update)day falls at position 200!? sorry for my english.