Targeted ads are becoming scarily accurate. This is due to your online behaviour being combed through by algorithms which are able to predict (or prescribe with high accuracy) what you'll be interested in. This is a dangerous game because you may find yourself buying things you don't need.
Big technology companies who collect this data use it to target ads to you, but they also sell this data to other companies for research. This is why you may be on one website looking at a specific pair of shoes and while on another website you see advertisement for them.
Subvert the algorithmic advertisement by click wrong ads.