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<style>
html {
  height: 100%;
}
html body {
  height: 100%;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}
html body .container-fluid.body-content {
  flex:1;
  width: 100%;
  overflow-y: auto;
}
header {
    background-color: #4C4;
    min-height: 50px;
    width: 100%;
}
footer {
    background-color: #4C4;
    min-height: 30px;
    width: 100%;
}

</style>
<html>

<body>
  <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" rel="stylesheet"/>
  <header>a</header>
  <div class="container-fluid body-content">

  </div>
  <footer>b</footer>
</body>
</html>