XHTML: Close Empty Tags
All empty tags must be closed. Include a space before the trailing "/>" of empty tags to ensure backward compatibility with the browsers.
These elements are all done the wrong way:
A break: ==> <br>
A horizontal rule: ==> <hr>
An image: ==> <img src="happy.gif" alt="Happy face">
These elements are done the correct way:
A break: ==> <br />
A horizontal rule: ==> <hr />
An image: ==> <img src="happy.gif" alt="Happy face" />