 <p>tinyMCE <a href="http://www.tinymce.com/wiki.php/Configuration%3avalid_elements" rel="nofollow">valid_elements</a> option allows to specify wide range of rules to 'normalize' the document: it's powerful, but it's quite strict in its syntax. Particularly speaking, one shouldn't use whitespace as additional separator of the rules. </p> <p>For example, to restrict valid elements to <code>&lt;p&gt;</code> and <code>&lt;br /&gt;</code> only, this line should be used:</p> <pre><code>... valid_elements: 'p,br' // not valid_elements: 'p, br' ... </code></pre>