HTML Checking for Large Sites

Padding properties, unline margin properties, don’t accept negative values.

CSS styles could not be parsed, check the indicated line to find what caused the parser to fail. Common causes are unclosed curly brackets or comments, missing semicolons or unexpected or empty properties.

The value break-word for the property word-break is deprecated, you should replace it with a valid value.

According to the CSS Text Module Level 3 spec:

For compatibility with legacy content, the word-break property also supports a deprecated break-word keyword. When specified, this has the same effect as word-break: normal and overflow-wrap: anywhere, regardless of the actual value of the overflow-wrap property.

The value specified for the transform CSS attribute is not valid.

The transform CSS property lets you rotate, scale, skew, or translate an element. It modifies the coordinate space of the CSS visual formatting model.

The ::file-selector-button has not been recognized by the W3C Validator. This seems to be a bug in the W3C Validator, which has already been reported.

The value specified for a width attribute in CSS is not valid.

The width CSS property sets an element’s width. There are many allowed values for this attribute, for example:

/* <length> values */
width: 300px;
width: 25em;

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

/* Keyword values */
width: max-content;
width: min-content;
width: fit-content(20em);
width: auto;

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

CSS can’t be properly processed because a computed style is missing a value it depends on.

CSS properties need to be separated by semicolons. Check for the missing semicolon between properties.

In the example below, a forgotten semicolon before the content property makes the CSS parser unable to understand the properties:

<style>
nice {
  z-index: auto 
  content: ""; 
  display: block; 
}
</style>

Fix it by including the forgotten semicolon like this:

<style>
nice {
  z-index: auto;
  content: ""; 
  display: block; 
}
</style>

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 specified CSS property is not valid.