HTML
You may be looking for the following:
- Help:HTML in wikitext — HTML tags in wikitext
- Help:Lint errors/obsolete-tag — for deprecated HTML elements (detected by Lint)
- HTML restriction — about restriction of HTML use in MediaWiki
- HTMLForm — class for handling user interface forms
- Manual:HTML templates — generate HTML content from Mustache templates
- HTML5 — using HTML5 features in MediaWiki
- Manual:Html.php — the file used in extensions.