Cafe-sciences.org W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
Duplicate attribute “xmlns:fb”.
Attribute “xmlns:fb” not allowed here.
Attribute “xmlns:addthis” not allowed here.
Attribute “xmlns:og” not allowed here.
Bad value “https://api.w.org/” for attribute “rel” on element “link”: The string “https://api.w.org/” is not a registered keyword.
No space between attributes.
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The “frameborder” attribute on the “iframe” element is obsolete.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.
The element “iframe” must not appear as a descendant of the “a” element.
Duplicate ID “ytplayer”.
Warnings:
Attribute with the local name “xmlns:fb” is not serializable as XML 1.0.
Attribute with the local name “xmlns:addthis” is not serializable as XML 1.0.
Attribute with the local name “xmlns:og” is not serializable as XML 1.0.
The “navigation” role is unnecessary for element “nav”.
The first occurrence of ID “ytplayer” was here.
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