var c = 0;
var s = 100;


$(function(){
var h = $('#personInner').height();
$('#down').click(function(){
c = ((c - s) < (h - 420) * -1) ? (h - 420) * -1 : c - s;
$('#personInner').animate({top:c}, 470 );
return false;					   
});

$('#up').click(function(){
c = ((c + s) > 0) ? 0 : c + s;
$('#personInner').animate({top:c}, 470 );
return false;					   
});

});