Browser can cache images, javascripts, css files on users hard drive and it can also cache Xml Http calls if the call is a Http Get. The cache is based on Url. If it's the same Url and it's cached on the computer then the response is loaded from cache, not from the server when it is requested again. Basically, browser can cache any Http Get call and return cached data based on Url. If you make a Xml Http call as Http GET and server returns some special header which informs the browser to cache the response; on future calls, the response will be immediately returned from the cache and thus save the delay of network roundtrip and download time.
