Your computer can't hear you. If you've entered a search for a cruise holiday, for example, it's going to use the data in the search to advertise high end holidays to you using pop -up ads. If you search for camping holidays, the sort of ads you're going to get are also hiking, walking and adventure holidays; outdoor wear, bikes, binoculars and travel insurance. If you've searched for camping holidays a day or two after looking at Per Una clothes, you'd get caravan holidays popping up, with walk-in showers, wide-fit shoes, varifocal glasses, and audio books e.g.
It's all about profiling. The same ads that you'd find in a Saga magazine are not going to pop up if a teenager profile has been picked up purely by the searches entered.
Try this: search teenage things on one computer, and then search grandparent things on another.