居中未知宽度的灯箱

Centering an unknown width Lightbox

我查看了其他一些线程,但似乎没有任何效果。我正在尝试将未知宽度的灯箱置于页面中央(水平)。任何帮助,将不胜感激。代码如下

HTML

<div class="backdrop"></div>
<div class="box">
    <div class="close">x</div>
    <img src="../pics/placeholder.png">
</div>

CSS

.backdrop {
  position: absolute;
  text-align: center;
  top: 0px;
  left: 0px;
  width: 100%;
  height: 100%;
  background: #000;
  opacity: .0;
  filter:alpha(opacity=0);
  z-index: 50;
  display: none;
}

.box {
  position: absolute;
  top: 20%;
  width: auto;
  height: auto;
  background: #ffffff;
  z-index: 51;
  padding: 2px;
  -webkit-border-radius: 5px;
  -moz-border-radius: 5px;
  border-radius: 5px;
  -moz-box-shadow: 0px 0px 5px #444444;
  -webkit-box-shadow: 0px 0px 5px #444444;
  box-shadow: 0px 0px 5px #444444;
  display: none;
}

.close {
  position: absolute;
  padding-left: 5px;
  padding-top: 5px;
  margin-left: 98%
  margin-top: 4px;
  cursor: pointer;
  font-family: sans-serif;
}

• 要使用 position: relative 水平居中元素,请使用:

.element {
    position: relative;
    display: inline-block;
    margin: 0 auto; /* We don't care about 0, but we do care about auto. */
}

• 要使用 position: absoluteposition: fixed 水平居中元素,请使用:

.element {
    position: fixed; /* Lightboxes usually use position: fixed. */
    left: 50%;
    transform: translateX(-50%);
}