W3C CSS Validation Web Standard

• W3C CSS Validation

CSS code can be automatically validated against a formal description of the CSS language. The formal description contains the grammar rules of CSS code, along with list of allowed properties.

Rules

• CSS validation error
• CSS hack or vendor extension
• CSS charset is unsupported
• Mismatched charsets
• Deprecated CSS property
• Unknown CSS property
• Property not allowed in at rule
• Vendor specific property or at-rule
• Unprefixed vendor property
• Unknown pseudo-class
• Unknown @media type
• Deprecated @media feature
• Unknown @media feature name
• Invalid @media feature value
• Unknown at-rule
• Invalid at-rule syntax
• Invalid @charset
• CSS @import must appear first
• Invalid CSS unit
• Invalid CSS identifier
• Invalid CSS selector
• Invalid CSS property value
• Too few CSS property values
• Too many CSS property values
• Invalid CSS color
• Invalid CSS URL
• Invalid CSS string
• Unterminated CSS comment
• Unexpected end of CSS
• MQ4 Deprecated @media type