*, *:before, *:after {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

body, html {
  margin: 0;
  padding: 0;
}

.block {
  margin-top: 30px;
  margin-bottom: 30px;
  min-height: 400px;
  background: #f0f0f0;
}

.clearfix::before,
.clearfix::after {
  width: 100%;
  display: table;
  clear: both;
  content: '';
}

.sticky-sidebar-css {
  position: sticky;
  position: -webkit-sticky;
  top: 0; /* required */
}