HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

CSS: “mso-X”: Property “mso-X” doesn't exist.

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.

Related W3C validator issues