Open linksinternal.html from and save it as fixed.html.  Imagine you wanted to have the heading always visible at the top of the page when you scroll down.  You might want that if it was the company name or a menu system.  There are four stages to make it workable.  First find the h1 element and change the opening tag to look like this:

<h1 style="position:fixed;">

Try the page and it looks awful because fixed positioned elements, like absolute, are ignored by the other elements on the page so you now have the main heading and other text in the same spot on the page.  Try scrolling.  To avoid that place extra padding on the body element to move the text down enough to clear the heading:

<body style="padding-top:30px;">

Try it but now the heading is not at the top where it was supposed to be so tell it to go to the top ignoring that padding (and to have no top margin while we are at it):

<h1 style="position:fixed;top:0; margin-top:0;">

One final improvement is to block the text as it scrolls under the heading by adding this to the inline styles for the heading:

background-color:white; width:100%;

This is not the best example as it would be better to put the h1 into a div and to style that.  That would also allow you to put more at the top.  This site currently uses fixed positioning for the menu, arrows and heading at the top of each page.

Hopefully this gives you some idea of the possibilities but also the potential problems of fixed positioning.  Be careful with it.