re: cacheability of favicons, this is basically a non-issue as the bandwidth-delay product of even a 10mbit/50ms connection is already 62 kB. Anything below this size on such a connection is likely to render faster than a separate request round-trip.
This raises to almost 1.2 MB with a 100mbit/100ms connection.
This raises to almost 1.2 MB with a 100mbit/100ms connection.