Thongtincongnghe.com W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
A document must not include more than one “meta” element with a “http-equiv” attribute whose value is “content-type”.
No “li” element in scope but a “li” end tag seen.
Element “div” is missing one or more of the following attributes: “role”.
Duplicate ID “system-message”.
An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.
Warnings:
The first occurrence of ID “system-message” was here.
Article lacks heading. Consider using “h2”-“h6” elements to add identifying headings to all articles.
Text run is not in Unicode Normalization Form C.
This document appears to be written in Vietnamese. Consider adding “lang="vi"” (or variant) to the “html” start tag.
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