Abstract: A method and system enables browsers to redisplay or refresh pages periodically while limiting retransmission of data to changing dynamic portions (data fields, dynamic content) of page files and avoiding retransmission of static portions of page files. Additional aspects include: a method of detecting when the infrequently-changing ‘skeleton’ parts of the page file have changed, thus avoiding having to re-transmit those parts with every update of the frequently-changing parts; a method of integrating the specification of add-on GUI ‘modules’ with ordinary web content written in HTML, thus reducing the effort needed to use the modules; and a method for a browser to instruct a web server to provide a specially modified version of a web page file. This reduces the amount of information that needs to be transmitted to refresh web pages periodically and facilitates incorporating defined GUI modules into HTML web pages.