Require use of known properties

Rule from css under compatibility category

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You have used a property that is not in the CSS specification. Happens to the best of us. Chances are this is simply pointing out a typo or spelling error. Any properties starting with '-' will be OK as they are considered vendor specific.

How to Fix

Use valid CSS or fix your typo. So if you've got .box{heigth: 10px} just fix it up.

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