HTML Guide
Rocket Validator checks HTML on your sites using the latest version of W3C Validator Nu HTML Checker, which is intended for HTML5 documents.
The page scanned is using an obsolete doctype, instead of the expected <!DOCTYPE html>.
Learn more:
Related W3C validator issues
Rocket Validator checks HTML on your sites using the latest version of W3C Validator Nu HTML Checker, which is intended for HTML5 documents.
The page scanned is using an “almost standards mode” doctype, instead of the expected <!DOCTYPE html>. While the almost standards mode was used in the transition to HTML5, you should consider moving to the HTML5 standard.
HTML documents are expected to start with a first line containing the Document Type Declaration, that defines the HTML version used. Since HTML5, it’s just <!DOCTYPE html>, which must appear before the start <html> tag.
Here’s an example of a minimal HTML5 document:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
</head>
<body>
<p></p>
</body>
</html>A missing or incorrectly placed <!DOCTYPE html> declaration at the very start of your HTML document causes this error.
The <!DOCTYPE html> declaration must be the very first thing in your HTML file, before any HTML code. This declaration tells the browser to use standards mode, ensuring reliable rendering. Without it, browsers may behave unpredictably or trigger quirks mode, and validators will issue an error.
Correct Example:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Valid HTML Document</title>
</head>
<body>
<p>Hello, world!</p>
</body>
</html>Incorrect Example (doctype missing):
<html lang="en">
<head>
<title>Invalid HTML Document</title>
</head>
<body>
<p>Hello, world!</p>
</body>
</html>Incorrect Example (doctype not at the very start):
Some misplaced text.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Invalid Placement</title>
</head>
<body>
<p>Hello, world!</p>
</body>
</html>Always ensure <!DOCTYPE html> is the first line.
The <!DOCTYPE html public "-//W3C//DTD HTML 4.0 Transitional//EN"> doctype triggers quirks mode in modern browsers and is not compliant with HTML5 standards.
The HTML5 specification requires the use of a simple doctype declaration, which ensures standards mode rendering. The correct doctype is <!DOCTYPE html>, which must appear at the very top of every HTML5 document. Legacy doctypes like HTML 4.0 Transitional are obsolete for modern web development and can cause inconsistent browser behavior.
Example of correct usage:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Valid HTML5 Doctype Example</title>
</head>
<body>
<p>Your content here.</p>
</body>
</html>Replace any legacy or malformed doctype with the above declaration to conform to current HTML standards.
HTML documents are expected to start with a first line containing the Document Type Declaration, that defines the HTML version used. Since HTML5, it’s just <!DOCTYPE html>, which must appear before the start <html> tag.
Here’s an example of a minimal HTML5 document:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
</head>
<body>
<p></p>
</body>
</html>All HTML documents must start with a <!DOCTYPE> (Document Type Declaration), that informs browsers about the type and version of HTML used to build the document. In HTML5, this is simply <!DOCTYPE html> and must appear at the start of the document.
Here is an example of a minimal HTML document, including the Document Type Declaration at its start:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
</head>
<body>
<p></p>
</body>
</html>The old <acronym> element in previous versions is now obsolete, in HTML5 you must use <abbr> instead.
The <big> tag is now obsolete. It was used to increase the size of text, you can do that using CSS instead. For example:
<p>Now this is <span style="font-size: larger;">big</span></p>The W3C Validator is indicating that the charset attribute on the link element is obsolete. According to modern HTML standards, the charset attribute should not be used on the <link> element, and instead, the character encoding should be specified via an HTTP Content-Type header on the server response of the resource.
Here’s how you can address and fix the issue:
1. Remove the charset attribute from the <link> element:
You should simply remove the charset attribute from the <link> element in your HTML file.
Before:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<link rel="stylesheet" href="styles.css" charset="UTF-8">
<title>Example Page</title>
</head>
<body>
<h1>Hello, World!</h1>
</body>
</html>After:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<link rel="stylesheet" href="styles.css">
<title>Example Page</title>
</head>
<body>
<h1>Hello, World!</h1>
</body>
</html>2. Set the charset using HTTP Headers:
To ensure that the correct character encoding is used, you should configure your web server to send the appropriate Content-Type header with the CSS file.
-
For Apache: You can modify the .htaccess file or the server configuration file.
<FilesMatch "\.css$"> AddCharset UTF-8 .css </FilesMatch> -
For Nginx: You can add the following directive to your server block or location block:
location ~* \.css$ { charset utf-8; } -
For Express.js (Node.js): You can set headers in your response:
app.get('/styles.css', function(req, res) { res.setHeader('Content-Type', 'text/css; charset=UTF-8'); res.sendFile(__dirname + '/styles.css'); });
A <script> element has been found that is using the now obsolete charset attribute. You can safely remove this attribute.
For example, this is using both type and charset attributes, with their default values. Both can be removed:
<script src="app.js" type="text/javascript" charset="UTF-8"></script>and just use this:
<script src="app.js"></script>