HTML Guide

The href attribute of an <a> element contains an invalid character, that should be properly encoded as a URI percent-encoded character.

<a> tags can be used to link to an email address using the mailto protocol in the href attribute. Ensure that there is no space in the email address.

<a href="mailto: liza@example.com">This is wrong as it contains an space</a>

<a href="mailto:liza@example.com">This is OK</a>

The W3C HTML Validator issue you encountered indicates that the URL provided in the href attribute of an anchor (<a>) element is not formatted correctly.

How to Fix the Issue

• Check the Protocol: For a valid URL, make sure that after https: there are two slashes (//).
• Update the URL: Correct the URL format to include the missing slash.

Example of Incorrect HTML

Here is an example of the code that would trigger the validation error:

<a href="https:/example.comf">Example</a>

Corrected HTML

Here’s how the corrected code should look:

<a href="https://example.com">Example</a>

Summary

Make sure that all URLs within href attributes are correctly formatted with both slashes following the protocol (https:// or http://).

The value provided on the type attribute of an a element is not a valid MIME type.

The type attribute expects a MIME type that hints at the linked URL’s format.

The type attribute on <a> elements, when present, gives a hint on the MIME type of the linked resource, for example:

<a href="application/pdf" src="book.pdf">Read our book</a>
<a href="image/jpeg" src="photo.jpeg">See a photo</a>

That is, we’re talking about the type of the linked resource, not the type of the <a> element, as it’s sometimes misunderstood. The following example is invalid because button is not a valid MIME type.

<a href="/order.php" type="button">Submit</a>

A button element, or an element with the role=button attribute, is not allowed to be nested inside an <a> element.

An <a> element cannot contain a descendant element with the attribute tabindex.

The itemscope attribute is a boolean attribute in HTML5, which means it does not take any values. Adding any value (such as true or false) will cause an error. When using boolean attributes, they should either be present or absent. If an attribute like itemscope is present, it is considered true.

Here’s how to correct the error:

Incorrect Usage:

<div itemscope="true">

Correct Usage:

<div itemscope>

Explanation:

• Simply including the itemscope attribute without any value is the correct way to use it.
• If you don’t want to use the itemscope attribute, just remove it from the tag.

The value contact is not a valid option for the autocomplete attribute on an <input> element.

The type dob is not valid for an input. If you want to build a date picker field, you can use the native HTML input elements with type date, datetime-local, or a generic text input decorated with JavaScript and CSS.

In HTML, the type attribute for the <input> element specifies the type of input control that is to be displayed. The type attribute can have values like text, password, email, date, etc. Using an unsupported or invalid value like dob (which presumably stands for “date of birth”) will cause this validation error.

Here’s an example of how you can correct this issue by using a supported type attribute value for the date of birth input:

<label for="dob">Date of Birth:</label>
<input type="date" id="dob" name="dob">

In this corrected example, we’ve used the type="date" attribute value for the date of birth input. This is a valid type for handling dates in HTML forms. Replace the input type with a supported type according to the specific data you need to capture.

Alternatively you can use a JavaScript library to build a date picker on a generic text input. For example, the popular bootstrap-datepicker library will generate a date picker around a text input.