function Scaler(id){
      var imgs=document.getElementById(id).getElementsByTagName('img'),index=0;
      var resize=function(to){
        var to=((to==='+1'?index+1:(to==='-1'?index-1:(isNaN(to)?index:to)))%imgs.length),to=to<0?imgs.length-1:to;
        if(to!=index)for(var i=0,l=imgs.length;i<l;i++){imgs[i].className=i==to?'bgshow':'';imgs[i].style.display='block'}
        var i=imgs[to],nw=Math.round(document.body.clientHeight*(i.offsetWidth/i.offsetHeight));
        i.style.width=(i.offsetWidth>i.offsetHeight&&document.body.clientWidth>nw)?'50%':nw+'px';
        return index=to;
      }

      if(window.attachEvent){window.attachEvent('onload',resize);window.attachEvent('onresize',resize)}
      else{window.addEventListener('load',resize,false);window.addEventListener('resize',resize,false)}
      return resize;
    };