var isIE = !!document.all;

var _picIndex=null;
var _picTimer=null;

function $(controlId){
    return document.getElementById(controlId) ;
}

function picGo(){
    if(_picTimer != null){
        clearTimeout(_picTimer);
    }
    setPicStatus();    
    _picIndex = (_picIndex==3?1:_picIndex+1);
    _picTimer = setTimeout('picGo()',3000);
}

function setPicStatus(){
    var picUrl = 'images/p' + _picIndex + '.jpg' ;
    $('picBox').setAttribute('src',picUrl);
    
    var classExp = (isIE?'className':'class');
    for(var loop=1;loop<=3;loop++){
        if(_picIndex!=loop)
            $('pic_'+loop).setAttribute(classExp,'a1');
        else
            $('pic_'+loop).setAttribute(classExp,'a2');
    }
}

function picIndexMouseOn(picIndex){
    if(_picTimer != null){
        clearTimeout(_picTimer);
    }
    _picIndex = picIndex ;
    setPicStatus();
}

function picShow(picIndex){
    _picIndex = picIndex ;
    picGo();
}

picShow(1);