This is a browser add-on written to help end-users reason about and quantify the enviromental impacts of their browsing habits. It was written specifically for Firefox web browsers.
This program is currently unreleased but if you want to try the alpha version, download the code and then point firefox to the about:debugging page. From there, choose "This Firefox" and then click on the "Load Temporary Add-On" button, which will prompt you to choose a file to load. Choose the 'manifest.json' file, and the program will be loaded into your browser. Click on the electrical tower pylon icon in the toolbar after browsing for awhile to see how much data you have downloaded since installing it.