||This MediaWiki page is inactive and kept for historical interest. It may document extensions or features that are obsolete and/or no longer supported. Do not rely on the information here being up-to-date.|
MediaWiki has delivered XHTML 1.0 Transitional code since version 1.3, with small fixes and improvements towards better compliance along the way. For a full discussion of XHTML, see Wikipedia's XHTML article. However since version 1.16 MediaWiki has switched to HTML5.
Benefits of XHTML compliance in MediaWiki 
- elements from different XML namespaces (such as MathML and Scalable Vector Graphics) can be incorporated within XHTML documents.
- despite being a separate specification, XHTML is viewed as the 'current' (most up-to-date) version of HTML.
- XHTML is required for many resource-constrained / small form factor browsers.
- much easier to transform (via XSLT, etc.) into other formats.
Negative aspects of delivering XHTML in MediaWiki 
- older browsers break when using XHTML mimetype.
- parsing of user-supplied XHTML would have to become much stricter, as badly formed markup can break an entire page.
Somewhat related settings :