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I'm looking in WMT at the crawl errors and I noticed that our website has gotten a lot of Not Found crawl errors that seem strange. A lot of these not found pages are Display URLs that I use in PPC advertising, but not actual redirects (i.e. explorica.com/EducationalTrips). When I looked at how these links were being found, the inbound links were coming from Nextag.com and monstermarketplace.com, two sites that our company has never had a relationship with. We're an educational travel company, so we'd have no reason to. When I followed the links, it looks like it's coming from their "Sponsored Links," but these aren't Google or Bing Ads. We don't even advertise on the content network. Example link: http://www.monstermarketplace.com/starters-and-alternators/alternator-motorola-style-12v-51a-10376 (the ads do rotate so my site might not appear when you check it out). Anyone ever had experience with this type of issue?