The YourAdvalue extension tries to detect and report how much the users cost for the advertisers, based on the ads that the user receives in real time. Every day, while browsing the web, ads are sent to our devices and browsers and shown in the websites we visit. Some of them are persistent and we encounter them every time we visit a specific website, but others are specifically tailored to meet our web searches, interests and hobbies, past browsing behavior, etc. For the latter type of ads to be tailored and delivered, the advertisers collect several types of data about each user and then use these data to send specific ads to the users-targets. But how much does it cost for the advertisers to send these targeted ads? In essence, how much does it cost for advertisers to collect all the needed data about each user, process them and use them for modeling the user's behavior and interests, and sending targeted ads to that user?