Center align a div horizontally and bottom of the page

There is an easy way to have the div position to the left or right to the screen with the use of fixed property. But how do you make a div horizontally center aligned and always be at the bottom of the page?

This will be of great useful if you want to make any popup div for display important messages or take any surveys etc. So here is a simple trick to show the content of a div horizontally aligned and always be at the bottom of the page...

HTML:
<div class="parent">
<div class="child">
Content here
</div>
</div>

CSS:
.parent{
position:fixed;
bottom:0px;
width:100%; //width should be 100%
}
.child{
width:300px; //min width should give to center the div.
margin:0px auto; //here it will make center
}

Position fixed will support modern browser including ie7, but for ie6 you have to use microsoft expressions to render the page as position fixed, as it will render wrongly. If you find any solutions without using expression in ie6, please explain use which will be helpful to others.