This is a notice message, recommendation in HTML. And an real HTML error in XHTML.
Add a ";" at the end of each entity.
Entity " " doesn"t end in ";"
BAD : Some &nsbp &nsbp spaces GOOD: Some &nsbp;&nsbp;spaces
W3C: entities: http://www.w3.org/TR/html4/sgml/entities.html
W3C HTML: remark about ";" http://www.w3.org/TR/html4/charset.html#entities