Not closing tags is now HTML5 valid for void elements (such like img
, br
...)
<meta charset="UTF-8">
Adding the closing />
is still valid, and in my personal opinion (only personal), it may get deprecated in a near future.
Void elements only have a start tag; end tags must not be specified for void elements.
Reference: W3C
EDIT: Of course, not closing tags is invalid for XHTML