This is due to:
- a bad order of the HTML tags
- or to an additional tag that should not be there
- or to a closing tags of an explitely or implicitely closed tag
replacing </p> by <br>
BAD (explicit close) <p>hello</p></p> GOOD <p>hello</p><br> BAD (implicit close) <p>abc<br><table>...</table></p> GOOD <p>abc<br></p><table>...</table>
In the above sample, the <p> tag is implicitely closed when a new "block-level" tag like <table> is opened. For more info, read the definition of <p>.
W3C block: http://www.w3.org/TR/html4/struct/global.html#block-inline