HTML CSS
(a quick guide)
<div class="tab"> <input id="tab-1" type="checkbox"> <label for="tab-1">FIRST</label> <div class="content">CONTENT</div> </div>
<div class="tab"> <input id="tab-2" type="checkbox"> <label for="tab-2">SECOND</label> <div class="content">CONTENT</div> </div>
HIDE CHECKBOX & CONTENT .tab input, .tab .content { display: none; }
SHOW CONTENT WHEN CHECKED .tab input:checked ~ .content { display: block; }
RESPONSIVE AUTOFIT .tab label, .tab .content { display: block; width :100%; }