Using <p> as a line break is discouraged. However, the closing </p> is optional in HTML 4.01. It is not optional in XHTML, of course.
Thanks for pointing that out, your are absolutely right... I code everything in XHTML, and that is what I was referring to.
Still however, using <p> tag for a line break in HTML, even if it is valid, is bad practice at a minimum.
His page most likely didn't validate because he is using XHTML 1.0 Transitional...