HTML Guide

The id attribute of an HTML element, used to identify the element when linking, scripting or styling, must be unique in the whole document and must not contain whitespace.

Technically, in HTML5, the value for an id attribute may contain any character, except whitespace characters. However, to avoid inadvertent errors, only ASCII letters, digits, _, and - should be used and the value for an id attribute should start with a letter.

The for attribute on a label element can’t be an empty string. This attribute is intended to specify which form element a label is associated with, and it must reference the ID of an existing form element. An empty string is neither a valid ID nor a meaningful association.

Explanation

• Invalid HTML: <label for=""></label>

The for attribute expects the value to be the ID of a form element, such as an input, textarea, select, etc.

How to Fix

1. Identify the Form Element: Find the form element (input, textarea, select, etc.) that the label is supposed to be associated with.
2. Assign an ID to the Form Element: Ensure the form element has a unique ID.
3. Modify the Label’s for Attribute: Set the for attribute of the label to match the ID of the form element.

Example

Before Fix

<form>
    <label for="">Username:</label>
    <input type="text" name="username">
</form>

After Fix

<form>
    <label for="username">Username:</label>
    <input type="text" id="username" name="username">
</form>

IDs for HTML elements can’t be blank.

The <label> element represents a caption in a document, and it can be associated with a form input using the for attribute, which must be an ID. Document IDs cannot contain whitespace.

Example:

<form>
  <label for="user_name">Name</label>
  <input type="text" id="user_name" />
</form>

A <pattern> element has been found with an invalid ID. Check the format of the ID and ensure it does not start with a digit, full stop (.) or hyphen (-).

The <pattern> element is used within <svg> elements, which use XML 1.0 syntax. That syntax specifies that valid IDs only include designated characters (letters, digits, and a few punctuation marks), and do not start with a digit, a full stop (.) character, or a hyphen-minus (-) character.

The id attribute is used to identify a single element within a document, and is required to be unique. Check the document for repeated IDs.

Element IDs in an HTML document must be unique. The HTML validator is indicating the first occurrence of an ID that is repeated. Check the details for that issue to see web pages affected, and the elements within them, to fix that ID repetition.

In the days before HTML5, named anchors were used as a way to provide a link to a specific section of a document, for example:

<h2>
  <a name="section-5">Section 5</a>
</h2>

Now in HTML5, the name attribute is obsolete for <a> tags, and instead, you can use the id attribute of any element (not just <a>) as a way to navigate directly to it, for example:

<h2 id="section-5">Section 5</h2>

The warning regarding the use of the name attribute on the img element arises because the name attribute is considered obsolete in modern HTML. Historically, name was used to identify form controls and some other elements, but now it’s replaced by more standardized attributes like id.

To resolve this issue, replace the name attribute with the id attribute. The id attribute provides a unique identifier for the element within the document, which can be utilized for styling, scripting, or linking using fragment identifiers.

Here is an example of how to make this change:

HTML with obsolete name attribute:

<img src="example.jpg" name="myImage" alt="Descriptive text">

Updated HTML using the id attribute:

<img src="example.jpg" id="myImage" alt="Descriptive text">

In this modification:

• The name="myImage" is replaced with id="myImage".
• The remaining attributes like src and alt are retained for specifying the image source and providing alternative text, respectively.

The id attribute should be unique within the document, which ensures that JavaScript or CSS can target the element efficiently.

The <option> element no longer accepts a name attribute, which is now obsolete.

Example:

<select id="pet-select">
    <option value="">--Please choose an option--</option>
    <option value="dog">Dog</option>
    <option value="cat">Cat</option>
    <option value="hamster">Hamster</option>
</select>