visit http://dancewithnet.com/lab/2009/css-opacity/#demo9 in IE8 standard mode
1. demo9's html: <span id="demo9">demo9</span>
2. YAHOO.util.Dom.get('demo9').setStyle('opacity','0.3');
3. demo9 isn't a layout element, and YUI set it {zoom:1;}, but zoom can't trigger layout in IE8 standard mode
so it's failed
the following is a successful method:
var setOpacity = function(el,i){
if(window.getComputedStyle){// for non-IE
el.style.opacity = i;
}else if(document.documentElement.currentStyle){ // for IE
if(!el.currentStyle.hasLayout){
el.style.zoom = 1;
}
if(!el.currentStyle.hasLayout){ //for IE8
el.style.display = 'inline-block';
}
el.style.filter = 'alpha(opacity='+ i * 100 +')';
}
}

pls visit demo12: http://dancewithnet.com/lab/2009/css-opacity/#demo12