jquery blockUI 正中显示

jquery blockUI 居中显示
               var __widowWidth = $(window).width();
var __popWidth = $("#Loading").width(); //Loading为要显示的div
var __left = (__widowWidth - __popWidth)/2 + 'px';
var __windowHeight = $(window).height();
var __popHeight = $("#Loading").height();
var __top = (__windowHeight-__popHeight)/2 + 'px';
$.blockUI({ message: $('#Loading'),
css:{
cursor: '',
                                                                           left:__left,width:__popWidth+'px',top:__top,position:'fixed', //居中
         border: 'none',                   // 无边界
         width:"100px"                 // 中间框框的宽度
    },
    overlayCSS:{cursor: ''}
});