Sure you can: <ad> <adsrc href="/ad/car" src="car.png" keyword="automobile"> <adsrc href="/ad/pet" src="pet.png" keyword="cat dog pets"> ... </

Sure you can: <ad> <adsrc href="/ad/car" src="car.png" keyword="automobile"> <adsrc href="/ad/pet" src="pet.png" keyword="cat dog pets"> ... </ad> Of course this "allows" ad blocking, so Google will come up with some reason to reject it, but it's a perfectly workable system.