Use HTML5 cache manifest to improve performance?

i was reading Dive into开发者_如何学Go HTML5: Offline web apps: Cache manifest when i got an idea. can i use it (HTML5 Cache Manifest) to cache files (eg. CSS/JS/Images/etc) for offline capability. but also for performance. user wont need to load those files when they visit your site again? or will it (files cached by cache manifest) work only in offline mode?

No, if the browser supports offline then it will cache all the files listed in the manifest and only update them when you change the manifest. Last year someone demonstrated a technique based on the manifest to overcome the 15K per item limit of the iPhone cache.