How do I monitor bandwidth use of specific websites? I'm using Chrome on SnowLeopard.  I use the www a lot.  I want to monitor how much bandwidth I use for all SE sites in one month.  I don't care how much bandwidth is used on any other website.

What is the easiest way to do this?

Best answer will be an accurate tool to measure; but a reasonable estimate is acceptable too.
Historygram is a neat extension for Safari, but it appears to only measure visits, not bandwidth. Feel free to email the author and ask if this extension could easily be modified to include bandwidth measurement.