A computerized method of content verification comprising using a server for receiving a first data from a host monitoring code embedded in a webpage or an application loaded from a content server and executed by a client device, the host monitoring code is executed by the client device during an execution of the webpage or the application which further embeds nesting element(s) for loading nested content from nested content server(s), the first data is indicative of the execution, receiving a second data indicative of the execution from a guest monitoring code embedded in the nested content, combining the first data and second data for compliance verification of the execution with one or more rules associated with the nested content and initiating action(s) according to the verification. Wherein the first data is not available to the guest monitoring code and the second data is not available to the host monitoring code.