X-prefetch-url: X-prefetch-referer: X-navid: (looks like a session key) X-from-url: X-to-url: X-is-toplevel: (numeric value) X-exclude-url: X-is-complete: 1 (complete in cache?)
I also see Proxy-Connection: keep-alive, but I usually have pipelining enabled.
Most proxy replies are earmarked Transfer-encoding: chunked (I can't see the data stream, but I assume it's compressed), and it sets keep-alive and Expires: options, as well as a Via: header.
I've seen at least three types of Via: header on the browser side:
Via: HTTP/1.1 GWA Via: HTTP/1.1 GWA (remote cache hit) Via: HTTP/1.1 FastNet (preload cache hit)
Server-side, you'll get an X-moz: prefetch header in requests for items that the webmaster designated, and an X-Forwarded-For: header and a hit from a Google IP address for "normal" navigation (unless I missed something). More on prefetch here.
There are significant problems with pre-fetching, so you might want to make sure you return a 403 access denied code for prefetch requests if you design public web applications.