is there an elegant way to determine the size of data downloaded from a website -- bearing in mind that not all requests will go to the same domain that you originally visited and that other browsers may in the background be polling at the same time. Ideally i'd like to look at the size of each individual page -- or for a Flash site the total downloaded over time.
I'm looking for some kind of browser plug-in or Fiddler script. I'm not sure Fiddler would work due to the issues pointed out above.
I want to compare sites similar to mine for total filesize - and keep track of my own site also.
Firebug and HttpFox are two Firefox plugin that can be used to determine the size of data downloaded from a website for one single page. While Firebug is a great tool for any web developer, HttpFox is a more specialized plugin to analyze HTTP requests / responses (with relative size).
You can install both and try them out, just be sure to disable the one while enabling the other.
If you need a website wide measurement:
Keep in mind that if you download / estimating a dynamic websites, you are dealing with what the website produces, not with the real size of the website on the server. A small PHP script can produce tons of HTML.