Advertising keeps this site and many of the websites and services you use free of charge. Google works hard to make sure that ads are safe, unobtrusive and as relevant as possible. For example, you won’t see pop-up ads on this site. Google terminates the accounts of hundreds of thousands of publishers and advertisers that violate their policies each year – including ads containing malware, ads for counterfeit goods or those that attempt to misuse your personal information.
Cookies help to make advertising more effective. Without cookies, it’s harder for an advertiser to reach its audience, or to know how many ads were shown and how many clicks they received.
Google store a record of the ads they serve in their logs. These server logs typically include your web request, IP address, browser type, browser language, the date and time of your request, and one or more cookies that may uniquely identify your browser. They store this data for a number of reasons, the most important of which are to improve their services and to maintain the security of their systems. They anonymise this log data by removing part of the IP address (after 9 months) and cookie information (after 18 months).