horizontal-tabs.css in Field Group 8.3

.horizontal-tabs {
  margin: 0 0 1em 0; /* LTR */
  padding: 0;
  border: 1px solid #ccc;
  position: relative; /* IE6/7 */
}

[dir="rtl"] .horizontal-tabs {
  margin: 0 0 1em 0;
}

.horizontal-tabs .horizontal-tabs-list {
  display: inline-block;
  margin: 0;
  border: 0;
  padding: 0;
  list-style: none;
  background-color: #eee;
  border-bottom: 1px solid #ccc; /* LTR */
  width: 100%;
  height: auto;
  clear: both;
}

[dir="rtl"] .horizontal-tabs .horizontal-tabs-list {
  border-right: 0;
  border-left: 1px solid #dedede;
}

.horizontal-tabs-panes .horizontal-tabs-pane {
  padding: 0 1em;
  border: 0;
  background-color: unset;
  box-shadow: unset;
}

.horizontal-tabs-pane > summary {
  display: none;
}

/* Layout of each tab */
.horizontal-tabs  .horizontal-tab-button {
  background: #eee;
  border-right: 1px solid #ccc; /* LTR */
  padding-top: 0;
  margin: 0;
  min-width: 5em; /* IE7 */
  float: left; /* LTR */
}

[dir="rtl"] .horizontal-tabs .horizontal-tab-button {
  border-right: 0;
  border-left: 1px solid #ccc;
  float: right;
}

.horizontal-tabs .horizontal-tab-button a {
  display: block;
  text-decoration: none;
  padding: 0.5em 0.6em;
}

.horizontal-tabs .horizontal-tab-button a:hover {
  outline: none;
  background-color: #fff;
}

.horizontal-tabs .horizontal-tab-button li:hover,
.horizontal-tabs .horizontal-tab-button li:focus {
  background-color: #ddd;
}

.horizontal-tabs ul.horizontal-tabs-list :focus {
  outline: none;
}

.horizontal-tab-button a:focus strong,
.horizontal-tab-button a:active strong,
.horizontal-tab-button a:hover strong {
  text-decoration: none;
  outline: none;
}

.horizontal-tab-button.selected {
  background-color: #fff;
  border-bottom: 1px solid #fff;
  margin-bottom: -1px;
}

[dir="rtl"] .horizontal-tab-button.selected {
  border-left-width: 0;
  border-right-width: 1px;
}

.horizontal-tabs ul.horizontal-tabs-list li a,
.horizontal-tabs ul.horizontal-tabs-list li.selected a {
  display: block;
  text-decoration: none;
  padding: 0.6em 1em;
  position: relative;
  top: 0;
}

.horizontal-tab-button .selected strong {
  color: #000;
}

.horizontal-tab-button .summary {
  display: block;
}

.horizontal-tab-button .summary {
  line-height: normal;
  margin-bottom: 0;
}

/**
 * tab content
 */
div.field-group-htabs-wrapper .field-group-format-wrapper {
  clear: both;
  padding: 0 0 0.6em;
}