Any suggestions? (yes, I guess I could put it in an external js file)
Don't forget to include both the opening <!-- and closing // --> comment tags, also noting that there must be a space after the opening comment, and another before the closing comment.
Any closing </bar> will "fool" the validator, and give an error. Closing tags within document.write statements need to be broken in two, in order to hide them from the validator, like "</" + "bar>" and so on.
Make sure that the element that you are including with the document.write is valid in that place in the HTML structure; that you are not trying to nest an element where it is not allowed.