HTML Guide
The attributes width and height on an iframe expect a valid positive integer without any decimals.
Here’s an example of incorrect code where decimals are being used for dimension attributes:
<iframe src="example.html" height="602.88" width="800.2"></iframe>Corrected code without decimals:
<iframe src="example.html" height="603" width="800"></iframe>
In the corrected code, the width and height values has been changed to a whole number, which conforms to the standard integer value expected by the W3C validator.
Learn more:
Related W3C validator issues
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 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 <img> elements expect a non-negative integer, so an empty string is not allowed. Either define the correct dimension, or remove this attribute.
The value used in the height attribute on element iframe is not a valid integer. Remove any leading or trailing spaces from the attribute value.
Here’s an example:
<iframe width="560" height="315" src="your-video-link" frameborder="0" allowfullscreen></iframe>The attributes width and height on an iframe expect a valid positive integer without any decimals.
Here’s an example of incorrect code where decimals are being used for dimension attributes:
<img src="photo.jpg" alt="Dog" height="602.88" width="800.2">Corrected code without decimals:
<img src="photo.jpg" alt="Dog" height="603" width="800">In the corrected code, the width and height values has been changed to a whole number, which conforms to the standard integer value expected by the W3C validator.
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.
Attribute values for width and height on the object element must be a valid integer (pixels), not a percentage.
In HTML5, the width and height attributes for the <object> element must be specified in pixels as an integer value, such as height="500". Using percentage values like height="100%" is not allowed in the attribute according to the HTML living standard and will trigger a validation error. To set a percentage height, use the CSS width and height properties instead.
Correct usage (pixels via attribute):
<object data="example.pdf" type="application/pdf" width="600" height="400"></object>Correct usage (percentage via CSS):
<object data="example.pdf" type="application/pdf" style="width: 100%; height: 100%;"></object>Example of a full valid HTML document using CSS for 100% height:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Object Height Example</title>
<style>
html, body {
height: 100%;
margin: 0;
}
object {
height: 100%;
width: 100%;
display: block;
}
</style>
</head>
<body>
<object data="example.pdf" type="application/pdf"></object>
</body>
</html>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" />The <table> element does not accept a height attribute. Use CSS instead.
The seamless attribute was proposed to be included in the HTML5 spec, but it wasn’t finally accepted, so it’s not a valid attribute for <iframe>.