Certapet.com W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
Bad value “https://api.w.org/” for attribute “rel” on element “link”: The string “https://api.w.org/” is not a registered keyword.
The element “button” must not appear as a descendant of the “a” element.
Duplicate ID “navbtn”.
Element “h1” not allowed as child of element “span” in this context. (Suppressing further errors from this subtree.)
The “frameborder” attribute on the “iframe” element is obsolete. Use CSS instead.
Element “h3” not allowed as child of element “span” in this context. (Suppressing further errors from this subtree.)
Element “h2” not allowed as child of element “span” 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The “center” element is obsolete. Use CSS instead.
Warnings:
The “banner” role is unnecessary for element “header”.
Document uses the Unicode Private Use Area(s), which should not be used in publicly exchanged documents. (Charmod C073)
The “navigation” role is unnecessary for element “nav”.
The first occurrence of ID “navbtn” was here.
The “contentinfo” role is unnecessary for element “footer”.
Consider using the “h1” element as a top-level heading only (all “h1” elements are treated as top-level headings by many screen readers and other tools).
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