CSS opacity - 实现图片半透明效果

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这个效果在 IE 和 Mozilla 浏览器上都可以工作，代码如下

<img alt="powerbookg4.jpg" src="archives/images/powerbookg4.jpg" width="250" height="60" style="-moz-opacity:0.5; filter:alpha(opacity=50);cursor:hand;" onmouseover="this.style.MozOpacity=1;
this.filters.alpha.opacity=100" onmouseout="this.style.MozOpacity=0.5;
this.filters.alpha.opacity=50">

在 IE 中需要通过 "filter" 来定义透明度 "opacity" ，而在 Mozilla 中是可以直接解析 "opacity", 所以如果要使得这个效果在两种浏览器中都得到支持，需要把两种设定都加进去。针对 IE 的设定： this.filters.alpha.opacity=50 　而针对 Mozilla 的设定：this.style.MozOpacity=0.5.