I think Google is intentionally giving only a certain number of visitors for my website - usually I have some average numbers for day from Google search - and some days I am getting some 2/3 of that number for some 5 hours - so I may think - a good day is coming - and then for several hours no visitors at all , at some time visitors from Google start coming again for a while, and then comes blackout again for several hours, and so on.... I see it almost regularly, it would hardly be explainable otherwise...Probably for some hours Google search is showing my results in good positions, and then shuffle everything around and what you could get during those hours, you get and then wait again.... What do you think?