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