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