When a context change is received , the placement and weight of {HEAD ~ the ads} are reevaluated 370 in accordance with {TAIL ~ the placement and weight rules} of the respective ads 
When a context change is received , the placement and weight of { HEAD ~ the ads } are reevaluated 370 in accordance with { TAIL ~ the placement and weight rules } of the respective ads
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH