HTML Checking for Large Sites
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<video>
elements accept a height
attribute to specify the width in CSS 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.
Here’s an example of setting width
and height
on a video
element.
<video controls width="640" height="480">
<source src="/media/cc0-videos/flower.webm" type="video/webm">
</video>
Related W3C validator issues
The controlslist attribute on the <video> element is experimental, and not yet valid in the current HTML5 standard, so you should use it with caution as it may not be supported by all browsers.
The <table> element does not accept a height attribute. Use CSS instead.
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" />
The attributes width and height of <iframe> 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 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 <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.
The attributes width and height on <img> elements define the dimensions of the image in CSS pixels, and expect a non-negative integer.
<video> elements accept a width attribute to specify the width in CSS 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.
Here’s an example of setting width and height on a video element.
<video controls width="640" height="480">
<source src="/media/cc0-videos/flower.webm" type="video/webm">
</video>
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" />
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