This is a really easy question, but I don't know the answer! Googleguy said that getting one's webserver to issue a "not modified since" in response to Googlebot can help reduce data transfer.
I have a website that I put onto a virtual host 2 months ago, and the logs show me 15% of hits generate a 304. However, Google seems to take about 75% of my site every day, and I get fresh dates every day for all of those, even though many aren't changing.
I've done a header server check and can see that it returns a 200 with the date last modified.
My question is this - what tool do I need to see whether my server is generating a 304 when it should be - it's doing some, I'm not sure it's doing enough! Or is Google fetching differently without a "modified since" nowadays?