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height attributes on
<iframe> elements expect a digit to indicate the number of pixels. Ensure that this attribute contains only digits.
<!-- 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
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.
The attributes width and height on <img> elements define the dimensions of the image in CSS pixels, and expect a non-negative integer.
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" />
<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%;">
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<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" />
When an img element has an empty alt attribute, its role is implicitly decorative, so it must not specify a role attribute.
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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.
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>
The src attribute on an <img> element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
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" />
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