The self-closing elements are covered in the style guide. In the [Elements and Attributes section](https://github.com/jquery/contribute.jquery.org/blob/master/pages/style-guide/html.md#elements-and-attributes) it says "Self-closing elements should not be closed." The [Encoding section](https://github.com/jquery/contribute.jquery.org/blob/master/pages/style-guide/html.md#encoding) and [Example section](https://github.com/jquery/contribute.jquery.org/blob/master/pages/style-guide/html.md#example) both show a `<meta>` tag without the closing slash.