In fiddler, is there any way of knowing if some piece of code ( jscript, jquery, css) are been loaded from local cache vs downloaded from the server. I think this may be represented by different color in web sessions, but wasn't able to find legend for these colors.
If you see 304 Not Modified responses, those mean that the client made a conditional request, and server is signalling "no need to download, you have the newest version cached". That's one "class" of cached responses.
However, for some entities, not even conditional requests are sent (Expires header is in the future, etc. - see RFC2616 ). Those would not show up in Fiddler at all, as there is no request at all - the client may assume that the cached version is fresh.
What you can certainly see are the non-cached resources - anything coming back with a response code from the 2xx range should be non-cached (unless there's a seriously misconfigured caching proxy upstream, but those are rare nowadays).
You could clear your caches, and open the page. Save those results. Then open the page again - see what's missing when compared to the first load; those are cached.