$(function() {
    $("#div3").animate(
        {top : "+=100"}, 500, function() {}
    );
});

$(function() {
    $('#div3')
    .css({
        // position the element off the top of the page
        top : ($('#div3').height() * -1) - $('#div3').offset().top
    }).animate(
        // animate to its natural resting place
        {top : 0}, 500, function() {}
    );
});