背景与边框

半透明边框

body {
  padding: 2em;
  background: url('https://template-static.oss-cn-hangzhou.aliyuncs.com/idea/stone-art.jpeg');
}

.box {
  border: 20px solid rgba(255, 255, 255, .5);
  background: white;
  background-clip: padding-box;
}

多重边框

body {
  background-color: blue;
  padding: 2em;
}

.box {
  background: #fff;
  border: 10px solid hsla(0, 0%, 100%, .5);
  background: yellowgreen;
  box-shadow: 
    0 0 0 10px #655,
    0 0 0 15px deeppink,
    0 2px 5px 15px rgba(0,0,0,.6);
  }