This add-on enables dragging scroll on the web pages in Firefox browser. you can enable that with pressing <CTRL>+<dubble-click> or
<ALT>+<dubble-click> or <SHIFT>+<dubble-click> on the web pages in firefox.
You can install this add-on on Firefox from here: https://addons.mozilla.org/en-US/firefox/addon/dragonweb/
enjoy study :)