裡邊的滾動圖片為什麼在FF中轉得很慢啊，在IE正常

Question

function Slider(args){
    //read & apply arguments
    this.args = args;
    this.setArgs();
    //store dom elements
    this.container = document.getElementById(args.containerid);
    this.contentWrapper = getElements('content_wrapper','DIV',this.container)[0];
    this.contentLists = this.container.getElementsByTagName('UL');
    //set up the slider
var slider = this;
    setTimeout(function(){slider.initialize()},750);
}/*  Argument Setup
    -------------- */
    Slider.prototype.setArgs = function(){
        //required arguments
        this.groupSize = this.args.groupsize;
        this.direction = this.args.direction;
        this.effectType = this.args.effect || false;
        
        //optional arguments
        this.hasGroupNav = (this.args.hasgroupnav === null) ? true : this.args.hasgroupnav; 
        this.hasLoop = this.args.hasloop || false;
        this.hasAutoAdvance = this.args.hasautoadvance || false;
        this.advanceSeconds = this.args.advanceseconds || 5;
        this.hasTabs = this.args.hastabs || false;
        this.tabs = this.args.tabs; //required for tabbed modules
        this.speed = this.args.speed || 7;
    }/*  Initialization
    -------------- */
    Slider.prototype.initialize = function(){
        this.setContext(0);     //set the context of the content initially displayed in the slider to the first list
        this.activeGroup = 1;   //set a flag used as a current group indicator
        this.assembleScrollControls();  //create a group of slider controls which applies to this content
        this.updateControlDisplay();     //update display of the controls to match behavior of this module;
        if(this.hasTabs) this.assembleTabs( );    //for sliders used to display more than one context of content, create the tab controls
        this.setupLayout();  //set up the layout properties constraining container and content list
        if(this.hasAutoAdvance) this.autoAdvance();     //if this slider autoadvances, begin the process
    }/*  Set the Context of Displayed Content
    ------------------------------------ */
    Slider.prototype.setContext = function(context_index){
        this.contentList = this.contentLists[context_index];    //set the active content list
        //capture useful properties of the content list
        this.contentItems = this.contentList.getElementsByTagName('li');
        this.numItems = this.contentItems.length;
        this.numGroups = Math.ceil(this.numItems/this.groupSize);
        this.itemWidth = this.getItemWidth();
        this.itemHeight = this.getItemHeight();
    }/*  Scroll Control Creation & Event Handling
    ------------------------------------- */
    Slider.prototype.assembleScrollControls = function(){
        var moduleObject = this;
        if( this.numGroups > 1 ){   //only create controls if they are needed
            //create & register handlers for next/previous controls
            this.nextTrigger = this.createTrigger('slide_control_next');
            this.prevTrigger = this.createTrigger('slide_control_previous');
            if(window.addEventListener){
                this.nextTrigger.addEventListener("click", function(event){ moduleObject.advance(1); }, false);
                this.prevTrigger.addEventListener("click", function(event){ moduleObject.retract(1); }, false);
            }
            if(window.attachEvent){
                this.nextTrigger.attachEvent("onclick", function(event){ moduleObject.advance(1); }, false);
                this.prevTrigger.attachEvent("onclick", function(event){ moduleObject.retract(1); }, false);
            }
            //create & register handlers for group nav
            if( this.hasGroupNav ){
                this.groupNav = this.createGroupNav();
                this.groupTriggers = this.groupNav.getElementsByTagName('A');
                for(var i=0; i<this.groupTriggers.length; i++){
                    if(window.addEventListener)
                        this.groupTriggers[i].addEventListener("click", function(event){ moduleObject.switchGroup(event); }, false);
                    if(window.attachEvent)
                        this.groupTriggers[i].attachEvent("onclick", function(event){ moduleObject.switchGroup(event); },false);
                }
            }
        }
    }