var floatingMenuId = 'sidebar';
var menuOriginalPos = 1;
var timer;
var duration = 30;

function floatingMenu(){
	var e = document.getElementById(floatingMenuId);
	var curtop = findPosY(e);
	var hasMoved = document.documentElement.scrollTop || document.body.scrollTop;
	//alert(hasMoved);
	if(hasMoved >= menuOriginalPos){
		e.style.top = (parseInt(hasMoved) - menuOriginalPos) + 'px';
	} else {
		e.style.top = '168px';
	}
	timer = setTimeout('floatingMenu()', duration);
}

// 以下的程式碼是從網路上找到的，回頭在找就找不到原網頁了。有人找到的話，記得告訴我，讓我把原始網頁給連上來。

function findPosX(obj){
var curleft = 0;
if(obj.offsetParent)
	while(1) 
	{
	  curleft += obj.offsetLeft;
	  if(!obj.offsetParent)
		break;
	  obj = obj.offsetParent;
	}
else if(obj.x)
	curleft += obj.x;
return curleft;
}

function findPosY(obj)
{
var curtop = 0;
if(obj.offsetParent)
	while(1)
	{
	  curtop += obj.offsetTop;
	  if(!obj.offsetParent)
		break;
	  obj = obj.offsetParent;
	}
else if(obj.y)
	curtop += obj.y;
return curtop;
}