HTML Checking for Large Sites

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

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.

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.

An invalid CSS property is being used. Properties starting with mso- are commonly defined by Microsoft products like Office and Outlook.

These properties, like mso-spacerun, mso-fareast-font-family, mso-bidi-font-weight, mso-margin-bottom-alt, mso-margin-top-alt and others starting with mso- are not standard CSS properties.