The meta element with a charset attribute represents a character encoding declaration.
meta.charset = empty & meta.charset.attrs
meta.charset.attrs = common.attrs & charset
The meta element is a void element. A meta element must have a start tag but must not have an end tag.
There must not be more than one meta element per document with a charset attribute.
If a document contains a meta element with a charset attribute, then the document must not contain a meta element in the encoding declaration state.