Caching an ASP Page
Some applications send pages through a proxy server, which acts on the behalf of client browsers to request pages from a Web site. In most instances the proxy server caches HTML pages to reduce the load on the server, and to improve the processing speed of the HTTP request. This usually works well for static content but is inappropriate for most dynamically generated ASP pages. You can, however, instruct a proxy server to cache an ASP page by setting the Response.CacheControl property to Public.
Source: Jason Fisher
By default the property is set to Private, which prevents the server from caching the page.
<% Response.CacheControl = "Public" %>