HTML Checking for Large Sites

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.

A CSS definition for an X property could not be understood by the parser. Check it to ensure that it’s well formed and that it contains an appropriate value.

The <table> element does not accept a height attribute. Use CSS instead.

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.

font-display isn’t a CSS property, it’s a descriptor for use with the @font-face at-rule.

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.

The max-width CSS property sets the maximum width of an element. It prevents the used value of the width property from becoming larger than the value specified by max-width.

This property can express a value in different units like px, em, % or ch, and keyword values, but auto is not an allowed value.

Some examples of valid values for max-width:

/* <length> value */
max-width: 3.5em;

/* <percentage> value */
max-width: 75%;

/* Keyword values */
max-width: none;
max-width: max-content;
max-width: min-content;
max-width: fit-content(20em);

/* Global values */
max-width: inherit;
max-width: initial;
max-width: revert;
max-width: unset;

The value specified for the min-height CSS attribute is not valid.