로딩 레이어 만들기

<script  type="text/javascript">
var timer_loading=null;
function loading_st(){
 var ct_left = (parseInt(window.screen.width)-450)/2;
 var ct_top = (parseInt(window.screen.height))/3;
 layer_str = "<div id='loading_layer' style='position:absolute; font-size:11pt; left:"+ct_left+"px; top:"+ct_top+"px; width:400px; padding:50px; text-align:center; vertical-align:middle; z-index:1000; font-weight: bold;'>로딩중입니다.</div>"
 document.write(layer_str);
 timer_loading = setTimeout('self.document.location!!.reload()',4000) //4초 동안 페이지 로딩이 완료 안되면 리로드 한다.);

 if(window.attachEvent){
 window.attachEvent('onload', loading_ed)
 }else{
 window.addEventListener('load', loading_ed, false)
 }
}
function loading_ed(){
 var ta =document.getElementById('loading_layer');
 ta.style.display='none';
 clearTimeout(timer_loading)
}
loading_st();
</script>