On non-void elements, self-closing tags (those that finish in "/>") are disliked by the Wikipedia W3C validator. (Elements that may never have any content are referred to as void elements.) Do they function properly in HTML5?
Several acceptable void element examples:
<img src="" />
<input type="text" name="username" />
Examples of non-void components that were rejected:
<div id="myDiv" />
<span id="mySpan" />
<textarea id="someTextMessage" />