{HEAD ~ Variations} in differences between target web site data values and corresponding average and bounding web site data values over time determines {TAIL ~ improvement} and success of the target web site 
determines
{ HEAD ~ Variations } in differences between target web site data values and corresponding average and bounding web site data values over time determines { TAIL ~ improvement } and success of the target web site
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH