29. A method of dynamically supplementing a web page loaded by a web browser from a web site, the method comprising: generating a tag via a tag generation tool, and communicating the tag to an operator of said web site, said tag adapted for incorporation into web page coding of the web site; receiving, over a network, a request generated by the browser in response to said tag being included in the web page; and responding to the request by causing the browser to load and execute an update handler, wherein execution of the update handler causes the browser to at least (a) analyze content of the web page and to determine that the web page includes a link that matches a pre-specified link signature of a catalog page, said link including an identifier of a product, (b) retrieve, based on said identifier of the product, catalog content associated with the product, wherein the catalog content is retrieved over a network from a content server that is separate from the web site, and (c) supplement the web page with the catalog content; wherein the method, including generating the tag, receiving the request, and responding to the request, is performed by a system that comprises at least one machine.
29. A method of dynamically supplementing a web page loaded by a web browser from a web site, the method comprising: generating a tag via a tag generation tool, and communicating the tag to an operator of said web site, said tag adapted for incorporation into web page coding of the web site; receiving, over a network, a request generated by the browser in response to said tag being included in the web page; and responding to the request by causing the browser to load and execute an update handler, wherein execution of the update handler causes the browser to at least (a) analyze content of the web page and to determine that the web page includes a link that matches a pre-specified link signature of a catalog page, said link including an identifier of a product, (b) retrieve, based on said identifier of the product, catalog content associated with the product, wherein the catalog content is retrieved over a network from a content server that is separate from the web site, and (c) supplement the web page with the catalog content; wherein the method, including generating the tag, receiving the request, and responding to the request, is performed by a system that comprises at least one machine. 31. The method of claim 29 , wherein causing the browser to load and execute the update handler comprises transmitting at least a portion of the update handler to the browser from the content server.