like in http://www.online-photoshoptutorials.com/2008/08/folding-corners.html
<div id="toolbar" style="position: fixed; bottom: 0px; left: 0px; width: 100%; color: #fff; background: #000;">
Toolbar Content
<!-- rest of your toolbar stuff here -->
</div>
That will create a div with a black background that remains at the bottom of the screen, regardless of browser resizing or scrolling. You can then style that div however you like.
you use the css directive for positioning
position: fixed;
more details and tinkering for the positioning