var fbMenuBar = (function(){
//statics
function getTags(dom,tagName){
if(!document.getElementsByTagName)
throw new Error("Your Brower doesn't support!");
if(!tagName || typeof tagName != "string")
throw new Error("Need TagName");
return dom.getElementsByTagName(tagName);
}

return function(sId){
//privates
var elebox = fbMenuBar.$(sId);
var btns = [];
var len;
var bgbtn = document.createElement("div");
bgbtn.className = "fbmenubg";
elebox.insertBefore(bgbtn,getTags(elebox,"ul")[0]);
var ftbtn = document.createElement("div");
ftbtn.className = "fbmenubtn";
var btnPos = bgbtn.offsetLeft;
var timer;
var speed = 20;

//constructor
if(!elebox)
throw new Error("There is no element called " + sId);

var list = getTags(elebox,"li");
len=list.length;

var table = document.createElement("table");
table.setAttribute("cellPadding","0");
table.setAttribute("cellSpacing","0");
table.setAttribute("border","0");
var tbody = document.createElement("tbody");
var tr = document.createElement("tr");

for(var i=0;i<len;i++){
var alink = document.createDocumentFragment();
alink.appendChild(list[i].firstChild);
var td = document.createElement("td");
td.appendChild(alink);
btns.push(td.firstChild);
list[i].innerHTML = td.firstChild.innerHTML;
tr.appendChild(td);
}

tbody.appendChild(tr);
table.appendChild(tbody);
ftbtn.appendChild(table);elebox.appendChild(ftbtn);

for(var i=0;i<len;i++){
list[i].index = i;
list[i].onmousemove = function(){
btnPos = this.index * 80 + 4;
};
}

//publics
this.showBtn = function(){
timer = setInterval(function(){
var oPosX = bgbtn.offsetLeft;
if(oPosX == btnPos) return;
var _speed = Math.round((btnPos - oPosX)/speed);
if(oPosX>btnPos&&_speed>-1) _speed = -1;
if(oPosX<btnPos&&_speed<1) _speed = 1;oPosX = oPosX + _speed;
bgbtn.style.left = oPosX + "px"; 
ftbtn.style.left = oPosX + 4 + "px";
table.style.marginLeft = -4 - oPosX  + "px";
},1);
}

this.setSpeed = function(newSpeed){
speed = newSpeed;
};

}
})();

fbMenuBar.$ = function(sId){
if(!document.getElementById)
throw new Error("Your Brower doesn't support!");
if(!sId || typeof sId != "string")
throw new Error("Need ID");
return document.getElementById(sId);
}

fbMenuBar.importCSS = function(sFilePath) {
if(!sFilePath || typeof sFilePath != "string")
throw new Error("Need file path");

var _head = document.getElementsByTagName("head")[0];
var _links = document.getElementsByTagName("link");

for(var i=0; i<_links.length; i++) {
if(_links[i].href.toLowerCase() == sFilePath.toLowerCase()) return;
}
var _css = document.createElement("link");
_css.setAttribute("type","text/css");
_css.setAttribute("rel","stylesheet");
_css.setAttribute("href",sFilePath);
_css.setAttribute("media","all");
_head.appendChild(_css);
return _css;
}