The W3C validator doesn't like self-closing tags (those that end with "
<img src="" />
<input type="text" name="username" />
<div id="myDiv" />
<span id="mySpan" />
<textarea id="someTextMessage" />
In HTML 4,
<foo / means
<foo> (which leads to
<br /> meaning
<title>hello</title>). Browsers did a very poor job of supporting this and the spec advises authors to avoid the syntax.
In HTML 5, the meaning of
<foo /> depends on the type of element.