Most Likely Cause and Fix
Your markup is lacking the
X attribute on an
element referred to by the relevant line and column number.
This attribute is required, it must not be omitted.
What This Error Means
There is a defined set of attributes for each HTML element. Some are required for your markup to be considered valid.
You have omitted the required
X attribute on an element
that requires it.
How To Fix It
The specific error message you encountered will refer to a line and column number. This will guide you to the exact point in your markup to which the error relates.
Find the relevant element and add the missing