HTML Guide

There is no attribute validate on the <form> element. Perhaps you meant novalidate?

If the novalidate attribute is present on a <form>, indicates that the form is not to be validated during submission.

For example, while this form has a required attribute on its input, it won’t be enforced because form validation has been disabled using novalidate:

<form novalidate>
  <label>City: <input required name="city"></label>
  <input type="submit" />
</form>

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.

All HTML elements may have the hidden boolean attribute set. When specified on an element, it indicates that the element is not yet, or is no longer, relevant, so browsers won’t render it.

Boolean attributes don’t accept values, its presence represents the true value and its absence represents the false value.

<!-- This is invalid because the hidden attribute should not have a value set -->
<div hidden="false"></div>

<!-- The correct way to hide a div is like this -->
<div hidden>This will be hidden</div>

<!-- And to show the element, we just don't hide it -->
<div>This won't be hidden</div>

The action attribute on a <form> element is not a required attribute, but if specified, must be a valid, non-empty URL. For example:

<form action="register.php">
</form>

The issue here is related to the encoding of URLs. In HTML and URLs, special characters that have specific meanings need to be encoded to ensure that the URL is interpreted correctly. This process converts characters to their percent-encoded form, where a character is replaced by % followed by two hexadecimal digits representing the ASCII code of the character.

Explanation:

• The action attribute of a <form> element specifies where to send the form-data when a form is submitted.
• If the URL contains special characters (e.g., spaces, <, >, #, %, etc.), they need to be percent-encoded. For instance, a space character is encoded as %20.
• In this case, the validator is complaining about a % sign that is not correctly followed by two hexadecimal digits, which typically happens if the URL was not properly encoded.

How to Fix:

1. Check the URL: Look for any raw special characters that need encoding.
2. Correctly Encode the URL: Use online tools or libraries that provide URL encoding support to ensure that the URL is correctly percent-encoded.

Example:

Suppose you have the following incorrect form tag:

<form action="submit%data.html">
  <!-- form elements here -->
</form>

The % in submit%data.html should be followed by two hexadecimal digits. If %data was intended to be a part of the URL, it should be encoded properly. Here is how to correct it:

<form action="submit%25data.html">
  <!-- form elements here -->
</form>

If % should represent data, replace % with %25, which is the percent-encoded form of %. Always verify each special character is correctly encoded. Using this approach ensures that the URL in the action attribute is valid according to HTML standards.

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>