HTML Guide
The at symbol (@) should be percent-encoded as %40 in order to include it at an href attribute.
Related W3C validator issues
An <a> element has been found with an invalid href attribute, containing more than one # adjacent character.
The # is used to separate the fragment part of an URI (typically used to indicate a section within a document). For example, this is a valid link to a URI containing a fragment:
<a href="https://example.com/faqs#pricing">pricing</a>The next example is invalid because it contains two adjacent # characters, so that the fragment part would be #pricing instead of pricing:
<a href="https://example.com/faqs##pricing">pricing</a>The href attribute of an <a> element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
The href attribute of the a element contains an invalid backslash character, which is not permitted in URLs.
According to the WHATWG HTML living standard, the href attribute must contain a valid URL. URLs use forward slashes (/) for path separators, and backslashes are not allowed as they can cause browsers and validators to misinterpret the address. Backslashes often arise when file paths are copied from Windows environments.
Correct Usage:
- Always use forward slashes / in your URLs.
- Remove any backslashes from href values.
Example of incorrect usage:
<a href="images\picture.jpg">View Picture</a>Corrected example:
<a href="images/picture.jpg">View Picture</a>An illegal character has been found for the “href” attribute on the “link” element.
To fix this issue, find the “link” element in question and make sure that the “href” attribute contains a valid URL without any illegal characters.
Here’s some example HTML code of a link element:
<!DOCTYPE html>
<html>
<head>
<title>My Webpage</title>
<link rel="stylesheet" href="styles/main.css">
</head>
<body>
<h1>Welcome to my webpage!</h1>
<p>Here is some content...</p>
</body>
</html>In the above example, the link element has a valid href attribute value of styles/main.css. Make sure that your href attribute values don’t contain any illegal characters.
<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://).
Empty href attributes like href or href="" are invalid in HTML and can cause unpredictable behavior.
According to the HTML specification, the href attribute in elements such as the a and link tags must contain a valid URL or fragment reference. An empty or omitted href results in the attribute being ignored or possibly causing compatibility problems, especially in older browsers. If you intend the link to do nothing, use href="#" and prevent the default action with JavaScript, or avoid making it a link if no action is necessary.
Valid HTML for a regular link:
<a href="https://example.com">Visit Example</a>Valid usage for a link that does nothing:
<a href="#" onclick="return false;">Do nothing</a>If the element should not be clickable, use a different tag such as span or button:
<span>Not a link</span>or
<button type="button">Not a link</button>Avoid writing:
<a href>Invalid link</a>or
<a href="">Invalid link</a>as these will produce the validation warning you saw.
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.