Principia.edu W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
Legacy doctype. Expected “<!DOCTYPE html>”.
When the attribute “xml:lang” in no namespace is specified, the element must also have the attribute “lang” present with the same value.
The “version” attribute on the “html” element is obsolete. You can safely omit it.
The “profile” attribute on the “head” element is obsolete. To declare which “meta” terms are used in the document, instead register the names as meta extensions. To trigger specific UA behaviors, use a “link” element instead.
Element “a” not allowed as child of element “ul” in this context. (Suppressing further errors from this subtree.)
An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.
The “frameborder” attribute on the “iframe” element is obsolete. Use CSS instead.
Bad value “tooltip” for attribute “rel” on element “a”: The string “tooltip” is not a registered keyword.
End tag for “body” seen, but there were unclosed elements.
Unclosed element “div”.
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