css 오퍼서티 적용 방법

<style type="text/css">
#infobg {
background-color:#333333;
width:100%;
height:100%;
position:absolute;
top:0px;
left:0px;
z-index:1;
filter:alpha(opacity=70);       /* For IE 5-7 */
   -ms-filter:"alpha(opacity=70)"; /* For IE 8 */
}
</style>