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HTML 

              
                <h1>Responsive Tabbed Content (aria-expanded)</h1>
<h2Each tabbed content element within the same page needs it´s own class= "group_x"</h2>
<div class="tab_bar">
  <button class="tabbedcontent__button group_1 default-tab" onclick="openTab(event, 'tab1-1', 1)">Tab 1.1</button>
  <button class="tabbedcontent__button group_1" onclick="openTab(event, 'tab1-2', 1)">Tab 1.2</button>
  <button class="tabbedcontent__button group_1" onclick="openTab(event, 'tab1-3', 1)">Tab 1.3</button>
</div>
<div id="tab1-1" class="tab_content group_1">
  <h3>Tab 1.1</h3>
  <p>Tab 1.1... Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
</div>
<div id="tab1-2" class="tab_content group_1">
  <h3>Tab 1.2</h3>
  <p>Tab 1.2... Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
</div>
<div id="tab1-3" class="tab_content group_1">
  <h3>Tab 1.3</h3>
  <p>Tab 1.3... Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
</div>
<br><br>
<h2>Another tabbed content thing:</h2>

<div class="tab_bar">
  <button class="tabbedcontent__button group_2 default-tab" onclick="openTab(event, 'tab2-1', 2)">Tab 2.1</button>
  <button class="tabbedcontent__button group_2" onclick="openTab(event, 'tab2-2', 2)">Tab 2.2</button>
  <button class="tabbedcontent__button group_2" onclick="openTab(event, 'tab2-3', 2)">Tab 2.3</button>
</div>
<div id="tab2-1" class="tab_content group_2">
  <h3>Tab 2.1</h3>
  <p>Tab 2.1... Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
</div>
<div id="tab2-2" class="tab_content group_2">
  <h3>Tab 2.2</h3>
  <p>Tab 2.2... Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
  </div>
<div id="tab2-3" class="tab_content group_2">
  <h3>Tab 2.3</h3>
  <p>Tab 2.3... Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
</div>
!

CSS 

              
                /* basic styles */
.tab_bar {
  overflow: hidden;
  background: #404040;
}
.tabbedcontent__button {
  background-color: inherit;
  float: left;
  border: none;
  outline: none;
  cursor: pointer;
  padding: 14px 16px;
  transition: 0.3s;
}
.tab_bar .tabbedcontent__button:hover { background-color: #000; }
.tab_bar .tabbedcontent__button.active { background-color: #000; }
.tab_content {
  display: none;
  padding: 10px;
  background: #eee;
}
/* tab menu: content fade */
.tab_content {
  animation: fadeEffect 2s;
}
@keyframes fadeEffect { from {opacity: 0;} to {opacity: 1;} }


/* just some more styles for demo */
.tab_bar button {
  font-family: Sans-Serif;
  font-size: 1.3rem;
  color: #fff;
}
.tab_content {
  background-color: #eee;
  font-family: Sans-Serif;
  font-size: 1.2rem;
  line-height: 1.2;
}
!

JS 

              
                function openTab(evt, tabcontentid, group_counter) {
  var i, tab_content, tabbedcontent__button;
  tab_content = document.getElementsByClassName("tab_content group_" + group_counter);
  for (i = 0; i < tab_content.length; i++) {
    tab_content[i].style.display = "none";
  }
  tabbedcontent__button = document.getElementsByClassName("tabbedcontent__button group_" + group_counter);
  for (i = 0; i < tabbedcontent__button.length; i++) {
    tabbedcontent__button[i].className = tabbedcontent__button[i].className.replace(" active", "");
    tabbedcontent__button[i].setAttribute("aria-expanded", "false");
  }
  document.getElementById(tabcontentid).style.display = "block";
  evt.currentTarget.className += " active";
  evt.currentTarget.setAttribute("aria-expanded", "true");
}
var defaulttabs = document.getElementsByClassName("default-tab");
for (var i = 0; i < defaulttabs.length; i++) {
    defaulttabs[i].click();
}
!
999px

Console