Webkikaku.co.jp W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
Saw “<?”. Probable cause: Attempt to use an XML processing instruction in HTML. (XML processing instructions are not supported in HTML.)
Almost standards mode doctype. Expected “<!DOCTYPE html>”.
The “profile” attribute on the “head” element is obsolete.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.
Attribute “content” not allowed on element “meta” at this point.
Bad value “content-style-type” for attribute “http-equiv” on element “meta”.
Bad value “content-script-type” for attribute “http-equiv” on element “meta”.
Bad value “https://api.w.org/” for attribute “rel” on element “link”: The string “https://api.w.org/” is not a registered keyword.
Element “script” must not have attribute “async” unless attribute “src” is also specified.
The “frameborder” attribute on the “iframe” element is obsolete. Use CSS instead.
The “scrolling” attribute on the “iframe” element is obsolete. Use CSS instead.
The “marginheight” attribute on the “iframe” element is obsolete. Use CSS instead.
The “marginwidth” attribute on the “iframe” element is obsolete. Use CSS instead.
An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.
Warnings:
Section lacks heading. Consider using “h2”-“h6” elements to add identifying headings to all sections.
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