CSS样式：
.overlay{position: fixed; z-index: 100000;width: 100%;height: 100%;top: 0;left: 0;filter: alpha(opacity=50);opacity: 0.5;overflow: hidden;background-color: #000;}
*html { background:url(*) fixed; }
*html body { margin:0; height:100%; }
*html .overlay{ position: absolute; left: expression(documentElement.scrollLeft + documentElement.clientWidth - this.offsetWidth); top: expression(documentElement.scrollTop + documentElement.clientHeight - this.offsetHeight); }
*html { background:url(*) fixed; }
*html body { margin:0; height:100%; }
*html .overlay{ position: absolute; left: expression(documentElement.scrollLeft + documentElement.clientWidth - this.offsetWidth); top: expression(documentElement.scrollTop + documentElement.clientHeight - this.offsetHeight); }
遮罩层HTML代码：
<div id="overlay" class="overlay" style="display:none"></div>
将上述代码添加到页面中，通过js函数控制“overlay”层的显示和隐藏来实现遮罩效果
