4mejores.com W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
Duplicate attribute “prefix”.
Bad value “” for attribute “href” on element “link”: Must be non-empty.
Bad value “https://api.w.org/” for attribute “rel” on element “link”: The string “https://api.w.org/” is not a registered keyword.
The text content of element “script” was not in the required format: Expected space, tab, newline, or slash but found “e” instead.
Attribute “name” not allowed on element “meta” at this point.
Element “meta” is missing one or more of the following attributes: “itemprop”, “property”.
The “center” element is obsolete. Use CSS instead.
The “scrolling” attribute on the “iframe” element is obsolete. Use CSS instead.
The “frameborder” attribute on the “iframe” element is obsolete. Use CSS instead.
The “allowtransparency” attribute on the “iframe” element is obsolete. Use CSS instead.
Warnings:
Consider avoiding viewport values that prevent users from resizing documents.
Empty heading.
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