About This HTML Issue
A <meta> element with a content attribute also needs an attribute that declares what that content means: name, http-equiv, property, or itemprop.
The content attribute only holds a value. Without one of the four declaring attributes, browsers and search engines have no way to tell whether that value is a page description, a viewport setting, an Open Graph property, or something else, so the tag does nothing. The validator usually reports this when the declaring attribute was misspelled (nme="viewport"), accidentally deleted while editing, or stripped out by a CMS or template.
Pick the attribute that matches the metadata you intend: name for document metadata such as description or viewport, http-equiv for pragma directives, property for Open Graph and other RDFa vocabularies, and itemprop for microdata.
Invalid example
This <meta> tag has a value but nothing that identifies it as the viewport configuration:
<head>
<meta charset="utf-8">
<meta content="width=device-width, initial-scale=1">
<title>Example page</title>
</head>
Valid example
Adding name="viewport" gives the value its meaning:
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Example page</title>
</head>
Find issues like this automatically
Rocket Validator scans thousands of pages in seconds, detecting HTML issues across your entire site.