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                <main class="wrap">
  <div class="mainContent">
    <p>Calc is very handy when you have a fixed width sidebar and a fluid content div. You can add a media query at some point to remove the floats and make both columns a 100% width.</p>
    <p>Browser support is pretty good. The unsupported browsers are Android < 4.4, IE < 9 and Safari/iOS < 6. However, you can always specify a fallback width for these browsers.</p>
    <p>For vendor prefixes, just webkit will do. The moz one is for Firefox 15 and below, so you shouldn't have to worry about that.</p>
  </div> <!-- /mainContent -->
  <div class="sidebar">
  </div>  <!-- /sidebar -->



                * {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
  box-sizing: border-box;

body {
  font-family: 'Poppins', sans-serif;
  line-height: 1.5;

.wrap {
  overflow: hidden;

.sidebar, .sidebar a {
  color: #fff;
.sidebar, .mainContent {
  padding: 10px;

.sidebar {
  background-color: #46bac9;
  width: 20em;
  float: right;

.mainContent {
  float: left;
    width: 65%; /* fallback for browsers not supporting calc */
    -webit-width: calc(100% - 20em);
  width: calc(100% - 20em);