When you bring a page to your screen, you'll see the whole page or, if the content is extensive, only a portion. Scroll bars will let you see the rest. Often the portion you see is the beginning of the page, but sometimes a link brings you content from the page's middle or end. A link can display a new page or display a different portion of the same page, in effect, automatically scrolling for you. For example, the beginning of a page might include a table of contents that links each chapter title to its respective content further down the page.
Scroll bars can appear along the right hand side or along the bottom of the screen.
To use the scroll bar you can click on the arrow button on each end or you can click and hold down the mouse button and drag the bar to the position where you wish to be. They are also very useful tools in maintaining state variables on the Web. A cookie is simply an HTTP header that consists of a text only string that gets entered into the memory of your browser. This string contains the domain, path, lifetime, and value of a variable that you set. If the lifetime of this variable is longer than the time the user spends at your site, then this string is saved to file for future reference.