HTML Guide
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>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>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>.
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>An end tag for X has been found that does not correspond to a previous open tag. This usually happens when you close the same tag twice, for example:
<ul>
<li>item</li>
</ul>
</ul>A <head> start tag has been found in an unexpected place in the document structure. Check that the <head> section appears before the <body> section, and that is not duplicated.
The <head> section of an HTML document is the container of metadata about the document, and must appear before the <body> section. A common cause of this issue is duplicated <head> sections.
Here is an example of a minimal HTML document structure:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
</head>
<body>
<p></p>
</body>
</html>A stray start tag <html> has been found in the document. As this tag defines the start of the whole HTML document, it should appear only once.
The “Stray start tag noscript“ error in the W3C HTML Validator indicates that the <noscript> tag has been used incorrectly or is placed in an invalid location within your HTML document.
The <noscript> tag is used to define alternative content for users who have disabled JavaScript in their browsers or for browsers that do not support JavaScript.
Common Causes:
- Position of <noscript>: The <noscript> tag should be placed correctly within sections where it is allowed.
- Nested Improperly: The <noscript> tag should not be placed inside other tags where it is not valid.
Correct Usage:
-
Within <head>:
<head> <title>Example Page</title> <script> // Some JavaScript code </script> <noscript> <style> /* Alternative styling if JavaScript is disabled */ </style> </noscript> </head> -
Within <body>:
<body> <h1>Welcome to the Example Page</h1> <script> // Some JavaScript code </script> <noscript> <p>JavaScript is disabled in your browser. Please enable JavaScript for the full experience.</p> </noscript> </body>
Fixing the Issue:
-
Inside Existing Tags: Ensure the <noscript> tag is not placed inside other tags where it cannot be parsed correctly.
<!-- Incorrect --> <div> <noscript> <p>JavaScript is disabled in your browser.</p> </noscript> </div> <!-- Correct --> <noscript> <div> <p>JavaScript is disabled in your browser.</p> </div> </noscript> -
Placement in Body or Head: Verify that the <noscript> tag is placed inside the <body> or <head> based on what content it’s providing a fallback for.
<!-- Incorrect (inside an illegal tag) --> <div> Some content <noscript><p>JavaScript is disabled in your browser.</p></noscript> </div> <!-- Correct --> <div>Some content</div> <noscript><p>JavaScript is disabled in your browser.</p></noscript>
Summary:
- Place <noscript> only within accepted sections (<head> or <body>).
- Avoid nesting <noscript> inside other tags improperly.
A <script> start tag has been found in an unexpected place in the document structure. Check that the <script> section appears within the <head> or <body> sections.
Here’s an example of a script inserted in the head of the document:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
<script>
console.log("Hello from the head");
</script>
</head>
<body>
<p></p>
</body>
</html>