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