I use Adblock Plus, a free app. My browser is Chrome. Occasionally I get directed to a site that requires me to switch it off, but not very often. With Chrome it is easy to switch it on and off.
Also worth noting here that we don't always see the same ads.. they are served up based on key words on a page, your general location or even past search results - or just randomly.
I'm seeing ads for a new Jeep which I am not shopping for and would not buy if I were in the market