[jQuery] weird animate() flicker in strict DTD in FF3

[jQuery] weird animate() flicker in strict DTD in FF3


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/
TR/html4/strict.dtd">
<script type="text/javascript" src="jquery-1.3.2.min.js"></script>
    $('.item').click(function(){
        $('#slider').animate({ // this element is inside another DIV that
has CSS overflow:hidden;
            top: '-200px'
        },1200);
}
In FF3, this causes a jaggedy sliding of the elements, very ugly.
Looks like the elements are literally jumping up and down while
sliding.
Not a problem in IE7, though...
Has anyone else seen this?