Something like this should get you started, you need to provide more info in the question to get a better answer, ie. what you've tried with code examples.
$('li').each(function(){
var randomTop = $('div').height()*Math.random(); //random top position
var randomLeft = $('div').width()*Math.random(); //random left position
$(this).css({ //apply the position each li
top : randomTop,
left : randomLeft
});
});