HTML Guide
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>The “Stray start tag “section”” error in the W3C HTML Validator typically occurs when a <section> tag appears in an unexpected location within your HTML document structure. This can happen if the <section> tag is not positioned correctly within the HTML5 content model.
Here’s a focused guide to fix this issue:
1. Check the Parent Element
Make sure the <section> tag is placed within elements where it is allowed. According to the HTML5 specification:
- A <section> element should be placed within the <body> tag.
- It should not be a direct child of an inline element or an element that does not support flow content.
2. Correct Nesting Within Elements
Ensure your HTML structure follows a logical hierarchy and that the <section> element is not incorrectly nested. This example shows a correct usage of the <section> tag:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Correct Usage of Section</title>
</head>
<body>
<header>
<h1>Page Title</h1>
</header>
<nav>
<!-- Navigation links -->
</nav>
<main>
<section>
<h2>Section Title</h2>
<p>Content for the first section.</p>
</section>
<section>
<h2>Another Section Title</h2>
<p>Content for the second section.</p>
</section>
</main>
<footer>
<p>Footer content</p>
</footer>
</body>
</html>3. Check for Mistaken Hierarchy
Verify whether the <section> tag is mistakenly placed inside elements that do not support it, such as directly inside a <p> tag or other inline elements. Correct any incorrect usage. For example this is incorrect usage because the <section> tag is placed after the closing <body> tag:
Incorrect:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Sample page</title>
</head>
<body>
<h1>Main title</h1>
<p>Some content</p>
</body>
</html>
<section>
<h2>Incorrect Section</h2>
<p>This section should not be after the closing body tag.</p>
</section>Correct:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Sample page</title>
</head>
<body>
<h1>Main title</h1>
<p>Some content</p>
<section>
<h2>Correct Section</h2>
<p>This section is fine.</p>
</section>
</body>
</html>
Summary
- Ensure your <section> tags are used within the <body> tag and other allowed elements.
- Maintain a logical hierarchy in your HTML document.
- Avoid placing <section> tags inside inline elements like <p>.
Following these steps should resolve the “Stray start tag “section”” error in your HTML document. Validate your HTML again after making these corrections to ensure the issue is resolved.
A <style> start tag has been found in an unexpected place in the document structure. Check that the <style> section appears within the <head> section.
Although in general it’s better to put your styles in external stylesheets and apply them using <link> elements, CSS styles can also be included inside a document using the <style> tag. In this case, it should be placed within the <head> section, like in this example:
<!DOCTYPE html>
<html>
<head>
<title>Test</title>
<style>
p {
color: #26b72b;
}
</style>
</head>
<body>
<p>This text will be green.</p>
</body>
</html>Ensure each column in your table has at least one <td> or <th> cell starting in it. This error often occurs when using the colspan or rowspan attributes incorrectly.
Example of correct usage:
<table>
<tr>
<th>Header 1</th>
<th>Header 2</th>
</tr>
<tr>
<td>Row 1, Cell 1</td>
<td>Row 1, Cell 2</td>
</tr>
<tr>
<td>Row 2, Cell 1</td>
<td>Row 2, Cell 2</td>
</tr>
</table>Incorrect usage example:
<table>
<tr>
<th>Header 1</th>
<th>Header 2</th>
</tr>
<tr>
<td colspan="2">Row 1, Cell 1</td>
</tr>
<tr>
<td>Row 2, Cell 1</td>
<!-- Missing cell in column 2 -->
</tr>
</table>The corrected version ensuring each column has a starting cell:
<table>
<tr>
<th>Header 1</th>
<th>Header 2</th>
</tr>
<tr>
<td colspan="2">Row 1, spanning both columns</td>
</tr>
<tr>
<td>Row 2, Cell 1</td>
<td>Row 2, Cell 2</td>
</tr>
</table>A <table> contains an incoherent number of cells on one of its columns. Check the structure of the table to find the invalid column.
Example of a valid table that defines in its header that the first column is 2 cells wide:
<table>
<thead>
<tr>
<th colspan="2">The table header</th>
</tr>
</thead>
<tbody>
<tr>
<td>The table body</td>
<td>with two columns</td>
</tr>
</tbody>
</table>This same table with an empty body will be invalid because the table header cannot match any body columns:
<table>
<thead>
<tr>
<th colspan="2">The table header</th>
</tr>
</thead>
<tbody>
</tbody>
</table>A <table> contains an incoherent number of columns on one of its rows. Check the structure of the table to find the invalid row.
For example, in the following table, the first <tr> row defines that it’s 2 columns wide, but the second <tr> row tries to use 5 columns by means of a colspan attribute:
<table>
<!-- This first row sets the table as 2 columns wide -->
<tr>
<td>First</td>
<td>Second</td>
</tr>
<!-- This second row tries to use 5 columns -->
<tr>
<td colspan="5">Wrong</td>
</tr>
</table><iframe> tags are used to embed another document within the current document. To indicate the contents of that nested document, you can either use the src attribute with an URL, or directly provide the contents with the srcdoc attribute. Examples:
<!-- This will embed a document by its URL -->
<iframe src="https://example.com"></iframe>
<!-- This will embed the contents provided in the srcdoc attribute -->
<iframe srcdoc="<p>some content</p>"></iframe>
<!-- This is invalid -->
<iframe><p>some content</p></iframe>This W3C HTML Validator issue indicates that you’ve placed text content directly inside a <select> element. According to the HTML specification, a <select> element can only contain <option> or <optgroup> elements, and no direct text nodes.
Here’s how to resolve this issue:
Steps to Fix:
- Remove Text Nodes: Ensure that you remove any text that exists directly inside the <select> tags.
- Use <option> Elements: If you want to display text as an option, use <option> tags for each selectable item.
Example of Incorrect Usage:
Here’s an example that generates the validator issue:
<select>
Please select an option:
<option value="1">Option 1</option>
<option value="2">Option 2</option>
</select>Corrected Example:
Here’s how to correct this by moving the text outside of the <select> element:
<label for="options">Please select an option:</label>
<select id="options">
<option value="1">Option 1</option>
<option value="2">Option 2</option>
</select>Summary:
- Always wrap any instructional or descriptive text outside of the <select> element.
- Use <option> tags to define the choices within the <select>.
The <ul> element is used to define unordered lists, where each element must be contained within a <li> element, like in this example:
<ul>
<li>first element</li>
<li>second element</li>
<li>third element</li>
</ul>Ensure that there’s no content inside the <ul> element that is not contained within a <li> element.
Sometimes this error comes when trying to give a title to the list, for example:
<ul>
Fruits
<li>Apple</li>
<li>Orange</li>
</ul>Instead, that title text should be outside the list, like:
<span>Fruits</span>
<ul>
<li>Apple</li>
<li>Orange</li>
</ul>Other times, this can come as the concatenation of <li> elements which results in something like:
<ul>
<li>First item</li>
<li>Second item</li>
<li>Third item</li>
</ul>Note how in this case that used to join the <li> is causing the problem, as it’s content that is not contained by a <li> element, as required by the <ul> element.
Read about Normalization in HTML and CSS.
The <th> HTML element defines a cell as a header of a group of table cells, and must appear within a <tr> element.
In the following example for a simple table, the first <tr> contains two <th> header cells naming the values for each column:
<table>
<tr>
<th>Name</th>
<th>Age</th>
</tr>
<tr>
<td>Liza</td>
<td>49</td>
<tr>
<tr>
<td>Joe</td>
<td>47</td>
</tr>
</table>The old <acronym> element in previous versions is now obsolete, in HTML5 you must use <abbr> instead.
<td> elements no longer accept an align attribute. This can be achieved using CSS like this:
<td style="text-align:center;">content</td>The aria-controls attribute identifies an element or elements in the same document whose contents or presence are controlled by the current element. It must point to existing elements by their ID. Check that the IDs contained in that property exist within the same document.
ARIA can express semantic relationships between elements that extend the standard parent/child connection, such as a custom scrollbar that controls a specific region, for example:
<div role="scrollbar" aria-controls="main"></div>
<div id="main">
. . .
</div>The aria-describedby attribute is used to indicate the IDs of the elements that describe the object. It should reference an existing ID on the same document, but that id was not found.
The aria-hidden attribute is redundat on an input of type hidden, so it should be removed.
Example:
<!-- Instead of this... -->
<input type="hidden" aria-hidden="true" id="month" value="10" />
<!-- You can just use this -->
<input type="hidden" id="month" value="10" />The aria-labelledby attribute establishes relationships between objects and their label(s), and its value should be one or more element IDs. It should reference an existing ID on the same document, but that id was not found.
The article role indicates a section of a page that could easily stand on its own on a page, in a document, or on a website, is implicit when using the <article> tag.
This role indicates a section of a page that could easily stand on its own on a page, in a document, or on a website. It is usually set on related content items such as comments, forum posts, newspaper articles or other items grouped together on one page. It can be added to generic elements like <div> to convey this role, for example:
<div role="article">
<h2>Heading</h2>
<p>Content...</p>
</div>Instead of using this role, it’s preferrable to use the native <article> element like this:
<article>
<h2>Heading</h2>
<p>Content...</p>
</article>The <header> HTML element represents introductory content, typically a group of introductory or navigational aids, and has an implicit role of banner, so specifying this role is redundant.
The following example represents a banner using the role attribute:
<div role="banner">
<img src="companylogo.svg" alt="my company name" />
<h1>Title</h1>
<p>Subtitle</p>
</div>By default, the HTML5 <header> element has an identical meaning to the banner landmark, unless it is a descendant of <aside>, <article>, <main>, <nav>, or <section>, at which point <header> is the heading for that section and not the equivalent of the site-wide banner.
This example uses the <header> element instead of the banner role:
<header>
<img src="companylogo.svg" alt="my company name" />
<h1>Title</h1>
<p>Subtitle</p>
</header>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><img> tags no longer accept a border attribute. This can be defined using CSS instead, for example:
<img src="..." alt="..." style="border:0;" />