message: Flexboxify generic error page
diff: width: 100%;
  height: 100%;
  background-color: #fff;
  + display: flex;
  + align-items: center;
  + justify-content: center;
  }
  .mx_GenericErrorPage_box {
  - position: absolute;
  - top: 0;
  - bottom: 0;
  - left: 0;
  - right: 0;
  - margin: auto;
  + display: inline;
  width: 500px;
  - height: 125px;
  + min-height: 125px;
  border: 1px solid #f22;
  padding: 10px 10px 20px;
  background-color: #fcc;
  