HTML Checking for Large Sites
Rocket Validator automatically checks your pages on the W3C Validator.
Bad value “Xpx” for attribute “width | height” on element “img | iframe”: Expected a digit but saw “p” instead.
The width
and height
attributes on <img>
and <iframe>
elements expect a digit to indicate the number of pixels. Ensure that this attribute contains only digits.
For example:
<!-- This is invalid because width is not a digit -->
<img width="225px" height="100px" alt="cat" src="cat.jpg" />
<!-- This is valid -->
<img width="225" height="100" alt="cat" src="cat.jpg" />
Related W3C validator issues
<img>
tags, used to include images on a document, require an alt
attribute to describe the contents of the image. This is essential for users that cannot see the image (like screen reader users), or as an alternate text when the image cannot be displayed. Example:
<img src="photo.jpg" alt="Person holding a cat" />
The <table>
element does not accept a height
attribute. Use CSS instead.
A start tag for <img>
has been found inside a <noscript>
section within the <head>
, where it’s not allowed. Consider moving it to the <body>
section.
The HTML <noscript>
element defines a section of HTML to be inserted if a script type on the page is unsupported or if scripting is currently turned off in the browser.
When JavaScript is disabled, the content inside <noscript>
will be used instead, so this content must fit within its parent section. As an <img>
tag is not allowed inside <head>
, this will raise an issue. Instead, consider moving the <noscript>
part to the <body>
section.
This issue is often related to 3rd party tracking pixels like the Facebook or LinkedIn conversion tracking pixels. For example, the Facebook pixel instructions tell you to insert it like this:
<html>
<head>
<script>
...some script...
</script>
<noscript>
<img src="..." />
</noscript>
</head>
<body>
...
</body>
</html>
Instead, consider moving the <noscript>
part inside the <body>
, where the <img>
makes sense to be inserted:
<html>
<head>
<script>
...some script...
</script>
</head>
<body>
...
<noscript>
<img src="..." />
</noscript>
</body>
</html>
Learn more:
The width
and height
attributes on <img>
elements expect a digit to specify the dimension in pixels. It should not contain units, letters or percent signs.
You can achieve this using CSS instead, for example:
<!-- Invalid syntax, the height attribute expects only digits -->
<img src="photo.jpg" alt="cat" height="auto" />
<!-- Valid syntax using CSS -->
<img src="photo.jpg" alt="cat" style="height: auto" />
Learn more:
The src
attribute on an <img>
element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
Learn more:
The src
attribute for <img>
tags is required, to define the source of the image, like in this example:
<img src="photo.jpg" alt="wombat" />
The attributes width
and height
of <img>
elements expect a non-negative integer, so an empty string is not allowed. Either define the correct dimension, or remove this attribute.
Learn more:
The <iframe>
element, used to embed another document inside the current document, accepts both attributes width
and height
which must be valid non-negative integers. Percentages are not allowed for these attributes.
Check the iframe spec.
The src
attribute on an element <img>
contains a {
curly bracket character, which is not allowed unless properly encoded.
Space characters are not allowed in src
attributes. Instead, they should be converted to %20
. In this example, the first line is invalid and the second is valid:
<img src="https://example.com/?s=some term" alt="description" />
<img src="https://example.com/?s=some%20term" alt="description" />
The src
attribute on an element <img>
contains a character that is not allowed, and should be encoded.
Some typical examples include the pipe character |
that should be replaced by its encoded alternative %7C
, and the left square bracket [
that needs to be encoded as %5B
.
The src
attribute on an <img>
tag is not allowed to contain space characters. You should replace them with “%20
“.
The attributes width
and height
on <img>
elements define the dimensions of the image in CSS pixels, and expect a non-negative integer.
Learn more:
The <iframe>
element, used to embed another document inside the current document, accepts both attributes width
and height
which must be valid non-negative integers. Percentages are not allowed for these attributes.
Check the iframe spec.
<img>
elements accept a width
attribute to specify the size in pixels. This value can only be an integer, it should not contain units or %
. If you need to specify a percentage width, you can do that with CSS:
<img src="photo.jpg" alt="red car" style="width:100%;">
The value specified for a width
attribute in CSS is not valid.
The width CSS property sets an element’s width. There are many allowed values for this attribute, for example:
/* <length> values */
width: 300px;
width: 25em;
/* <percentage> value */
width: 75%;
/* Keyword values */
width: max-content;
width: min-content;
width: fit-content(20em);
width: auto;
/* Global values */
width: inherit;
width: initial;
width: revert;
width: unset;
Learn more:
<img>
tags used to display images require the attribute src
to indicate the source of the image, for example <img src="/img/photo.jpg" />
.
<img>
tags no longer accept a border
attribute. This can be defined using CSS instead, for example:
<img src="..." alt="..." style="border:0;" />
A single <img>
element is used to embed an image, so adding the img
role to it is redundant.
The ARIA img role can be used to identify multiple elements inside page content that should be considered as a single image. These elements could be images, code snippets, text, emojis, or other content that can be combined to deliver information in a visual manner, for example:
<div role="img" aria-label="Description of the overall image">
<img src="graphic1.png" alt="">
<img src="graphic2.png">
</div>
Learn more:
Both <table>
and <td>
elements no longer accept a width
attribute. Instead, you should use CSS as in this example:
<table style="width:100%;">
<tr>
<td style="width:50px;">Name</td>
</tr>
</table>
Check the HTMLImageElement.srcset guide to learn about the correct usage of the srcset
and sizes
attributes.
25,000 HTML checks per month. Is that enough for your site?
Save time using our automated web checker. Let our crawler check your web pages on the W3C Validator.