1. A method for detecting display of content by a browser, comprising: sending a request for a web page identified by a first universal resource locator from a content display site to a content provider server via a public computer network; receiving an HTML file from the content provider site at the content display site, the HTML file including at least one computer executable display instruction that causes display of content associated with the HTML file and providing access to at least one computer executable monitoring instruction that causes display of the content to be detected at the content display site; executing the at least one computer executable display instruction at the content display site to cause display of the content; executing the at least one computer executable monitoring instruction received via the HTML file at the content display site, the at least one monitoring instruction performing monitoring responsive to an event notification passed from a host environment at the content display site to cause generation of a data signal indicating that the content was displayed; and transmitting the data signal from the content display site to a remote site which is different from the content provider site and which did not transfer the HTML file from the content provider site to the content display site.