HTML Checking for Large Sites
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The <center> tag is no longer valid in HTML, you should use CSS instead, for example:
<p style="text-align:center">this text will be centered</p>Related W3C validator issues
The <table> element does not accept a height attribute. Use CSS instead.
To query for the size of the viewport (or the page box on page media), the width, height and aspect-ratio media features should be used, rather than device-width, device-height and device-aspect-ratio, which refer to the physical size of the device regardless of how much space is available for the document being laid out. The device-* media features are also sometimes used as a proxy to detect mobile devices. Instead, authors should use media features that better represent the aspect of the device that they are attempting to style against.
The width media feature describes the width of the targeted display area of the output device. For continuous media, this is the width of the viewport including the size of a rendered scroll bar (if any).
In the following example, this media query expresses that the style sheet is only linked if the width of the viewport 768px maximum:
<link rel="stylesheet" media="only screen and (max-width: 768px)" href="styles.css">To query for the size of the viewport (or the page box on page media), the width, height and aspect-ratio media features should be used, rather than device-width, device-height and device-aspect-ratio, which refer to the physical size of the device regardless of how much space is available for the document being laid out. The device-* media features are also sometimes used as a proxy to detect mobile devices. Instead, authors should use media features that better represent the aspect of the device that they are attempting to style against.
The width media feature describes the width of the targeted display area of the output device. For continuous media, this is the width of the viewport including the size of a rendered scroll bar (if any).
In the following example, this media query expresses that the style sheet is only linked if the width of the viewport is greater than 768px:
<link rel="stylesheet" media="only screen and (min-width: 768px)" href="styles.css">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.
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The value on the display property is not valid.
The display CSS property sets whether an element is treated as a block or inline element and the layout used for its children, such as flow layout, grid or flex.
The specified CSS filter is not a standard one, and may only work in some browsers.
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font-display isn’t a CSS property, it’s a descriptor for use with the @font-face at-rule.
The value passed to the font-size property is invalid, probably missing the amount of px.
The font-size CSS property sets the size of the font, and this size can be expressed in different units, like em, % or px.
Example:
<!DOCTYPE html>
<html>
<head>
<title>Font-size Example</title>
<style>
p {
font-size: 16px;
}
</style>
</head>
<body>
<p>This is an example of a paragraph with a font-size of 16px.</p>
</body>
</html>This issue is a false positive by the W3C validator, fixed in the latest versions of Nu Validator.
The value revert is indeed a valid value for the CSS property font-size.
The @import CSS rule can be used to import a style sheet into another style sheet. It must appear at the top of the document, and after any @charset declaration.
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