用JavaScript实现仿Windows关机效果

                     this.prepareIE('100%', 'hidden');
                     this.setScroll(0,0);
                     this.hideSelects('hidden');//隐藏所有的<select>标记
              }
              //调用该类中的displayLightbox方法
              this.displayLightbox("block");
      },

      prepareIE: function(height, overflow){
            bod = document.getElementsByTagName('body')[0];
            bod.style.height = height;
            bod.style.overflow = overflow;

            htm = document.getElementsByTagName('html')[0];
            htm.style.height = height;
            htm.style.overflow = overflow; 
      },

      hideSelects: function(visibility){
           selects = document.getElementsByTagName('select');
           for(i = 0; i < selects.length; i++) {
                   selects[i].style.visibility = visibility;
            }
      },

      getScroll: function(){
            if (self.pageYOffset) {
                    this.yPos = self.pageYOffset;
            } else if (document.documentElement && document.documentElement.scrollTop){
                    this.yPos = document.documentElement.scrollTop;