css+filter实现简单的图片透明效果

<style type='text/css'>
/透明20%/
.opacity-20 {
filter:alpha(opacity=20); /支持IE浏览器的filter/
-webkit-filter:opacity(0.2); /支持chrome浏览器filter/
}
/不透明/
.opacity-100 {
filter:alpha(opacity=100);
-webkit-filter:opacity(1);
}
</style>
<script language="javascript">
function makevisible(cur,which){
//交替设置不带透明度和带透明度的css
//完成鼠标移进图片则不透明显示，鼠标移出则带透明度显示
if (which==0) {
cur.className = 'opacity-100';
}else{
cur.className = 'opacity-20';
}
}
</script>
<img src="final.bmp" border=1 onMouseOver="makevisible(this,0)" onMouseOut="makevisible(this,1)" alt="">