Deprecation: #24387 - TypoScript option config.xhtmlDoctype=xhtml_2¶
See Issue #24387
The TypoScript option
config.xhtmlDoctype = xhtml_2 is marked for removal in CMS 8, due to the W3C decision to
fully work on HTML5 instead of XHTML2. See http://www.w3.org/MarkUp/ and http://www.w3.org/News/2010.html#entry-8982
for more details.
Any TYPO3 installation with TypoScript that relies on
config.xhtmlDoctype = xhtml_2.
Use other doctypes like html5 to render the frontend of the TYPO3 site.