HTML Checking for Large Sites

The <script> tag allows authors to include dynamic scripts and data blocks in their documents. When the src is present, this tag accepts a type attribute which must be either:

• an empty string
• text/javascript (that’s the default, so it can be omitted)
• module

Examples:

<!-- This is valid, without a type it defaults to JavaScript -->
<script src="app.js"></script>

<!-- This is valid, but will warn that it can be omitted -->
<script type="text/javascript" src="app.js"></script>

<!-- An empty attribute is valid, but will warn that it can be omitted -->
<script type="" src="app.js"></script>

<!-- The module keyword is also valid as a type -->
<script type="module" src="app.js"></script>

<!-- Any other type is invalid -->
<script type="wrong" src="app.js"></script>
<script type="text/html" src="app.js"></script>
<script type="image/jpeg" src="app.js"></script>

The <table> element does not accept a height attribute. Use CSS instead.

The <textarea> element does not have a type attribute.

The HTML <textarea> element represents a multi-line plain-text editing control, and is useful when you want to allow users to enter a sizeable amount of free-form text, for example a comment on a review or feedback form.

The value rocketlazyloadscript used in a <script> tag is not a valid one according to the HTML specification. It is introduced by the WP Rocket Wordpress extension.

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>

The value used to define the type of a link is not valid. You’re probably using a URL instead of a valid type.

Example of a valid type:

<link rel="icon" type="image/png" href="favicon.png">

The specified type for an script element is not a valid MIME type as it’s missing a subtype.

A MIME type most-commonly consists of just two parts: a type and a subtype, separated by a slash (/) — with no whitespace between, for example:

text/javascript

input elements can be of different types but zip is not one of the allowed. Consider using a generic type like text instead.

A CSS definition for background-image could not be understood by the parser. Check its definition to ensure that it’s well formed and that it contains an appropriate value.