function rollLine(ul, delay, speed, lineHeight) {
	var slideBox = (typeof ul == 'string')?document.getElementById(ul):ul;
	if(slideBox==null) return;
	var delay = delay||1000;
	var speed=speed||20;
	var lineHeight = lineHeight||20;
	var tid = null, pause = false;
	var start = function() {
		tid=setInterval(slide, speed);
	}
	var slide = function() {
		if (pause) return;
		slideBox.scrollTop += 2;
		if ( slideBox.scrollTop % lineHeight == 0 ) {
			clearInterval(tid);
			slideBox.appendChild(slideBox.getElementsByTagName('ul')[0]);
			slideBox.scrollTop = 0;
			setTimeout(start, delay);
		}
	}
	slideBox.onmouseover=function(){pause=true;}
	slideBox.onmouseout=function(){pause=false;}
	setTimeout(start, delay);
}