$(function(){
	var imgNum = 4;
	var imgSize = 800;
	var time = 3000;
	var current = 1;
	setInterval(function(){
		if( current < imgNum ) {
			current++;
	$("#banner ul").animate({
				marginLeft : parseInt($("#banner ul").css("margin-left"))-imgSize+"px"
			},"slow");
		} else {
			 $("#banner ul").animate({
				marginLeft : parseInt($("#banner ul").css("margin-left"))+(imgSize * (imgNum-1))+"px"
			},"slow");
			current = 1;
		}
	}, time);
});