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The only permitted value for the xmlns attribute is http://www.w3.org/2000/svg.
The namespace declaration for an <svg> element is provided by the xmlns attribute like this:
<svg xmlns="http://www.w3.org/2000/svg">
<!-- more tags here -->
</svg>
Although using https in the URL looks like it’s going to be more secure, in fact this URL is not used to connect it to, only to declare the namespace.
Learn more:
Related W3C validator issues
The attribute xmlns:serif is not valid. Check this guide for more information on this issue.
The attribute xmlns:serif is not a valid namespace. This attribute is set by Affinity Designer on SVG exports.
The only permitted value for the xmlns:link attribute is http://www.w3.org/1999/xlink.
Although using https in the URL looks like it’s going to be more secure, in fact this URL is not used to connect it to, only to declare the namespace.
A <pattern> element has been found with an invalid ID. Check the format of the ID and ensure it does not start with a digit, full stop (.) or hyphen (-).
The <pattern> element is used within <svg> elements, which use XML 1.0 syntax. That syntax specifies that valid IDs only include designated characters (letters, digits, and a few punctuation marks), and do not start with a digit, a full stop (.) character, or a hyphen-minus (-) character.
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/)
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