Use of Method Overrides for Dynamically Changing Visible Page Content

A tag/content management system delivers customized content and/or program instructions to a user terminal. The system may deliver several groups of program executable instructions, including instructions that are global to all web domains controlled by a client server and those that are specific to a web page/group of web pages. The program instructions and/or content may also be delivered to the user terminal based on the evaluation of one or more conditions, including those related to the location of the user terminal, various HTTP header fields, the presence of specific HTML objects in a web page accessed by the user terminal, and the screen resolution of the user terminal, among other things.