I have always wanted to know how much data my browser is downloading , for me to view a particular web page .I always use opera for browsing , one of the reasons being it tells me the amount of data downloaded .To view this data, when a webpage is loaded, do the following,
Open opera (This is for version 9).
Go to Tools > Appearance.
Then go to the Toolbars tab and then you will be able to see a Progress Bar dropdown box.
By default it is set to Simple.
Select pop-up at bottom from the dropdown list and click the OK button.