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