Re:If-Modified-Since, User-Agent (Score 2)

In a lot of cases, it doesn't matter if the client supplies If-Modified-Since headers, or If-None-Match headers either. Slashdot is a prime example. You can supply all of the bandwidth reducing headers you want but slashdots server will give you the full feed every single damn time. Servers should also be gzipping their output, but most don't. Slashdot sure doesn't. Slashdot's rss feed would go from 12K to 3K if they did (I checked). Most of those 12K full feed results would be reduced to about 200 bytes if they honored the caching headers.