A system and method for preserving POST data on a server system are presented. Embodiments of the present invention include a method for preserving POST data comprising using a generic cache agent to intercept a POST request made by a client for a resource accessible from a server, creating a URI unique to the POST request, storing the URI and POST data associated with the POST request in a cache memory, redirecting the client to an authentication URL, and after authentication, retrieving the POST data from the cache memory, creating an HTML page, the HTML page comprising the POST data, and serving the HTML page to a web server. In another embodiment of the present invention, a cache engine clears stale POST data through a LRU (least recently used) cache mechanism. The present invention provides a generic cache engine that can be plugged into any web server running any kind of web application.