brexes on "reload content without reloading page(prevent header and footer from reloading)"

Thank you, but I still want only a code.. like this one but unfortunately I don't know how to use it and what changes should be made and where to locate it:

<script>
$(function(){
$('#content').load('/php/twitter.php');
$('#nav a').click(function(){$('#nav li').removeClass('on');
$(this).parent('li').addClass('on');
var page = $(this).attr('href');
$('#content').load('/php/' + page + '.php');
return false
;})
;});
</script>

Hope you help me :/