HTML Checking for Large Sites
Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.
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
<?...>tags on server scripting languages like PHP, like
- [freeCodeCamp: How to Use SVG Images in CSS and HTML]https://www.freecodecamp.org/news/use-svg-images-in-css-html/)
Related W3C validator issues
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.
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.
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