Did you get this message after
validating the page? If so, then you probably have mixed HTML coding with XHTML coding.
HTML version sample:
HTML Code:
<meta name="Description" content="Your description">
<meta name="Keywords" content="Your set of keywords for the page">
Reference:
Meta Tags - HTML Meta Tags
XHTML version sample:
HTML Code:
<meta name="Description" content="Your description" />
<meta name="Keywords" content="Your set of keywords for the page" />
There's a space and slash at the end of the XHTML sample.