Animations, whether created with CSS or performed by JavaScript, generate lots of repaint/reflow. It is thus better to use instant rather than animated changes in order to use less CPU resources.
Avoid fade in/fade out JavaScript effects in sliders. Instead of:
<script>
$('a').click(function () {
$('#foo').fadeIn();
});
</script>
write:
<script>
$('a').click(function () {
$('#foo').show();
});
</script>