To accommodate the surge in scrolling in an Internet world, most mice now include a scroll wheel (or something similar) so you don't have to use the scroll bar. You can use this wheel in Firefox to scroll pages, but it also does so much more:
The mouse pointer must be over the Web site for each of the tricks below to work.
Going back and forth: To navigate backward and forward through recent browsing history, hold Shift while scrolling the wheel down (to go back) or up (to go forward). Each tick of the wheel takes you backward or forward one page.
Enlarging or shrinking text: To enlarge or shrink text on a page, hold Ctrl (or on a Mac) while scrolling the wheel down (to enlarge) or up (to shrink). Each tick of the wheel enlarges or shrinks the size of the text by about 20 percent.
This change will affect future Web sites you visit in the same tab or window. To reset the text size to normal, go to View Text Size Normal, press Ctrl+0 (or +0 on a Mac), or just browse in a different tab or window.
Scrolling one line at a time: By default, Firefox respects your system settings and usually scrolls about four lines at a time. If you want to focus on a document line by line, you can hold down Alt (or Option on a Mac) while scrolling the wheel.
Scrolling pages more smoothly with Smooth Scrolling: By default, Firefox scrolls a page in notches — that is, it bumps the page up or down a certain amount each time you scroll. Some people might find this behavior jerky when reading a document line by line. You can turn on smooth scrolling in the Advanced category of the Options window, as I describe in Chapter 16, to have Firefox slide pages up or down more smoothly each time you scroll. If you previously browsed in Internet Explorer, you might feel more comfortable with smooth scrolling because Internet Explorer uses it.
Scrolling up and down a page quickly with autoscrolling: If your scroll wheel doubles as a button, you can use it to scroll a page quickly and even automatically. Move the mouse pointer to a dead part of the page (somewhere that isn't a link) and hold down the wheel button. An icon overlays the spot you clicked. Now, still pressing the wheel button, move your mouse up and down to scroll the page much faster than usually. Alternatively, you can release the wheel button as soon as you see the icon, move the mouse up or down, and leave it there. Firefox scrolls the page automatically. If you don't like autoscrolling and find yourself activating it frequently, you can disable it in the Advanced category of the Options window, as I describe in Chapter 16.
Some mice don't support this feature even if they have a scroll wheel that acts as a button.