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:

• [freeCodeCamp: How to Use SVG Images in CSS and HTML]https://www.freecodecamp.org/news/use-svg-images-in-css-html/)