This error occurs when the property name inside an attribute isn’t allowed.
If you are getting this type of error “Disallowed attribute or attribute value present in HTML tag.” like below the screenshot.
For example, In select tag, if you are creating the mid attribute. The validation error comes due to the attribute that you are using for creating. Please see the below
For this, you need to remove this mid attribute once you remove mid attribute then check on this website – https://validator.ampproject.org/ is your page Valid or not
That’s it for this tutorial!