给最大的父元素去定位
$('.we').click(function(){
$('.login').show();
ceshi();
})
function ceshi(){
var setOff = function(){
var $box = $(".login");
$box.css({
"position":"relative",
"left":(($(window).width()-$box.width())/2),
"top":$(window).scrollTop()+(($(window).height() -$box.height())/2 )
})
}
setOff();
$(window).resize(function(){setOff()})
}
