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HTML Guide

Free site validation

Find out what web pages on your sites are affected by HTML issues.

Saw “<?”. Probable cause: Attempt to use an XML processing instruction in HTML. (XML processing instructions are not supported in HTML.)

A tag starting with <? has been found within the document, but it’s not supported. Probable causes can be:

  • Copy-pasting the contents of an SVG file. If you do that, you should only paste the <svg>...</svg> part, but not the first line with <?xml...>.
  • Unprocessed <?...> tags on server scripting languages like PHP, like <?php>

Learn more:

Related W3C validator issues