Full XHTML 1.0 Strict validation of tinyMCE output
Note that this is done by removing all invalid elements and attributes, so then part of the buttons become useless.
A solution I am researching is to create a filter that replaces attributes with classes so that css could be used. For example replacing <p align="center"> with <p class="text-align_center">.
So in the mean time what I've done is added the following code to my theme's template.php. Replace my_theme's_name with your theme's name :-).
<?php
function my_theme's_name_tinymce_theme($init, $textarea_name, $theme_name,
$is_running) {
if (isset($init)) {
switch ($theme_name) {
case 'advanced':
$init['extended_valid_elements'] =
array('a[accesskey|charset|class|coords|dir<ltr?rtl|href|hreflang|id|lang|name|onblur|onclick|ondblclick|onfocus|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|rel|rev|shape<circle?default?poly?rect|style|tabindex|title|target|type], abbr[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], acronym[class|dir<ltr?rtl|id|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], address[class|align|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], applet[align<bottom?left?middle?right?top|alt|archive|class|code|codebase|height|hspace|id|name|object|style|title|vspace|width], area[accesskey|alt|class|coords|dir<ltr?rtl|href|id|lang|nohref<nohref|onblur|onclick|ondblclick|onfocus|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|shape<circle?default?poly?rect|style|tabindex|title|target], base[href|target], basefont[color|face|id|size], bdo[class|dir<ltr?rtl|id|lang|style|title], big[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], blockquote[dir|style|cite|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], body[alink|background|bgcolor|class|dir<ltr?rtl|id|lang|link|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onload|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|onunload|style|title|text|vlink], br[class|clear<all?left?none?right|id|style|title], button[accesskey|class|dir<ltr?rtl|disabled<disabled|id|lang|name|onblur|onclick|ondblclick|onfocus|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|tabindex|title|type|value], caption[align<bottom?left?right?top|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], center[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], cite[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], code[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], col[align<center?char?justify?left?right|char|charoff|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|span|style|title|valign<baseline?bottom?middle?top|width], colgroup[align<center?char?justify?left?right|char|charoff|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|span|style|title|valign<baseline?bottom?middle?top|width], dd[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], del[cite|class|datetime|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], dfn[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], dir[class|compact<compact|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], div[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], dl[class|compact<compact|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], dt[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], em/i[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], fieldset[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], font[class|color|dir<ltr?rtl|face|id|lang|size|style|title], form[accept|accept-charset|action|class|dir<ltr?rtl|enctype|id|lang|method<get?post|name|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|onreset|onsubmit|style|title|target], frame[class|frameborder|id|longdesc|marginheight|marginwidth|name|noresize<noresize|scrolling<auto?no?yes|src|style|title], frameset[class|cols|id|onload|onunload|rows|style|title], h1[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], h2[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], h3[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], h4[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], h5[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], h6[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], head[dir<ltr?rtl|lang|profile], hr[align<center?left?right|class|dir<ltr?rtl|id|lang|noshade<noshade|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|size|style|title|width], html[dir<ltr?rtl|lang|version], iframe[align<bottom?left?middle?right?top|class|frameborder|height|id|longdesc|marginheight|marginwidth|name|scrolling<auto?no?yes|src|style|title|width], img[align<bottom?left?middle?right?top|alt|border|class|dir<ltr?rtl|height|hspace|id|ismap<ismap|lang|longdesc|name|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|src|style|title|usemap|vspace|width], input[accept|accesskey|align<bottom?left?middle?right?top|alt|checked<checked|class|dir<ltr?rtl|disabled<disabled|id|ismap<ismap|lang|maxlength|name|onblur|onclick|ondblclick|onfocus|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|onselect|readonly<readonly|size|src|style|tabindex|title|type<button?checkbox?file?hidden?image?password?radio?reset?submit?text|usemap|value], ins[cite|class|datetime|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], isindex[class|dir<ltr?rtl|id|lang|prompt|style|title], kbd[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], label[accesskey|class|dir<ltr?rtl|for|id|lang|onblur|onclick|ondblclick|onfocus|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], legend[align<bottom?left?right?top|accesskey|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], li[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title|type|value], link[charset|class|dir<ltr?rtl|href|hreflang|id|lang|media|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|rel|rev|style|title|target|type], map[class|dir<ltr?rtl|id|lang|name|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], menu[class|compact<compact|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], meta[content|dir<ltr?rtl|http-equiv|lang|name|scheme], noframes[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], noscript[class|dir<ltr?rtl|id|lang|style|title], object[align<bottom?left?middle?right?top|archive|border|class|classid|codebase|codetype|data|declare|dir<ltr?rtl|height|hspace|id|lang|name|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|standby|style|tabindex|title|type|usemap|vspace|width], ol[class|compact<compact|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|start|style|title|type], optgroup[class|dir<ltr?rtl|disabled<disabled|id|label|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], option[class|dir<ltr?rtl|disabled<disabled|id|label|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|selected<selected|style|title|value], p[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], param[id|name|type|value|valuetype<DATA?OBJECT?REF], pre/listing/plaintext/xmp[align|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title|width], q[cite|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], s[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], samp[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], script[charset|defer|language|src|type], select[class|dir<ltr?rtl|disabled<disabled|id|lang|multiple<multiple|name|onblur|onchange|onclick|ondblclick|onfocus|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|size|style|tabindex|title], small[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], span[align<center?justify?left?right|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], strike[class|class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], strong/b[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], style[dir<ltr?rtl|lang|media|title|type], sub[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], sup[class|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title], table[align<center?left?right|bgcolor|border|cellpadding|cellspacing|class|dir<ltr?rtl|frame|height|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|rules|style|summary|title|width], tbody[align<center?char?justify?left?right|char|class|charoff|dir<ltr?rtl|id|lang|onclick|ondblclick|onkeydown|onkeypress|onkeyup|onmousedown|onmousemove|onmouseout|onmouseover|onmouseup|style|title|valign<baseline?bottom?middle?top], td[abbr|align<center?char?justify?left?right|axis|bgcolor|char|charoff|class|colspan