HTML Guide for content-type

A document must not include both a “meta” element with an “http-equiv” attribute whose value is “content-type”, and a “meta” element with a “charset” attribute.

charset
meta
http-equiv
content-type
utf-8

In order to define the charset encoding of an HTML document, both of these options are valid, but only one of them must appear in the document:

<!-- This is the preferred way -->
<meta charset="UTF-8">

<!-- This is the older way, also valid -->
<meta http-equiv="content-type" content="text/html; charset=UTF-8">