More on why Etags matter
Just found this link lurking around in my news reader at work:
From that table you can see that about three out of every four requests resulted in a 304. That represents a large savings in bandwidth and computation time and is done without turning on caching explicitly. That is, I have no Cache-Control: headers which would probably increase the savings even more. You can also see that my log statistics package was under-reporting the hits and that I am receiving not 100,000, but over 200,000 hits a week.
