Scroll bars
These run vertically at the right of the screen, and sometimes horizontally
at the bottom of the screen. These allow you to
scroll
or move the current Web page up and down, and from left to right by clicking your
mouse on anywhere on the scroll bar.
Your
Web browser
is unable to display an entire
Web page
on your screen at a time. The scroll bars are very useful for moving around
the current Web page.
Scroll bars also contain:
Scroll arrows
The vertical scroll bar has the up and down arrow, and the horizontal scroll bar has the
left and right arrow. You can click on these with your mouse to scroll the
current Web page.
Scroll boxes 
are on each scroll bar and indicate your position on the current Web page.