Navigating the screen can sometimes be a bother, especially if you want to scroll to a section in a very, very, very long page. Using the scroll bar can be inefficient. Wouldn't you like to do it by moving the mouse?...

[edit] Steps

Examine your mouse. If it has the middle wheel, then continue. If it doesn't, then get a new mouse.
Push down on it.
Remember where your mouse was, some arrows should be, either 2 or 4 arrows.
Navigate around the screen, as you should be able to by now.
Note that where the mouse was it will leave an imprint. Move the mouse back & it will stop.

[edit] Tips

If you want to control the speed then the further away the mouse is from the original point the faster it goes, the closer it is the slower it goes etc.
If you middle-click and it has four arrows, you can also move your mouse left or right and it will still scroll.