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