title: How to center modal window in css+html?
body: <p>How to center vertical modal window with such css style:  </p>
  
  <pre><code>.inquiry_form_container {
    left: 50%;
    margin-left: -375px;
    width: 750px;
    top: 150px;
    position: fixed;
    z-index: 10001;
    background: #fff;
    border: 1px solid #cccccc;
    display: block;
    -webkit-box-shadow: 0 0 10px #cccccc;
    -moz-box-shadow: 0 0 10px #cccccc;
    -o-box-shadow: 0 0 10px #cccccc;
    box-shadow: 0 0 10px #cccccc;
  }
  </code></pre>
  
  <p>it's has a non known height, how to do, that that window will be with same margins from top and bottom?</p>