There are 4 states to the position property:
static
absolute
relative
fixed
Unless you specify elements are generally positioned using static. An absolute position element is positioned relative to the first parent element that has a position other than static. If no such element is found, the containing block is <html>. This means it will position relative to the browser window. To solve this create a relative position like this:
<div style="position: relative;">
</div>
Within this you can then use absolute positioning based on this container
Examples
Forcing somthing to a fixed position on the screen
position:absolute;
bottom:0;