I don't know how many of you are buying ads on exchanges, on a large scale or any scale, but this might be interesting to know. Whenever you directly buy media on a website, you get to know where your banner is, check if it's running, maybe test it through proxies, etc. But when buying in bulk, you just rely on outside reporting, especially on blind, Run Of Network, media buying. Well, the thing is, not everyone online is a straight arrow (shocking, right?!), so if you see numbers that just don't add up, you may want to consider what's in this article and check for hidden ads, possible clickjacking. I mean face it, if your ad get 1-2% CTR everywhere else, but suddenly skyrockets to 10,000 clicks with a whopping 50% CTR, you haven't designed the world's best ad, you're getting ripped off by someone who thinks you're paying for clicks! Best case scenario, you aren't, you're paying for impressions, but it's like a Russian Roulette. Anyway, here's the article, enjoy http://www.spider.io/blog/2013/04/at-least-two-percent-of-monitored-display-ad-exchange-inventory-is-hidden/