99percentinvisible.org 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.
An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.
Duplicate ID “Architecture”.
Duplicate ID “Infrastructure”.
Duplicate ID “Cities”.
Duplicate ID “Objects”.
Duplicate ID “Sounds”.
Duplicate ID “Visuals”.
Duplicate ID “Technology”.
Duplicate ID “History”.
Warnings:
Section lacks heading. Consider using “h2”-“h6” elements to add identifying headings to all sections.
The first occurrence of ID “Architecture” was here.
The first occurrence of ID “Infrastructure” was here.
The first occurrence of ID “Cities” was here.
The first occurrence of ID “Objects” was here.
The first occurrence of ID “Sounds” was here.
The first occurrence of ID “Visuals” was here.
The first occurrence of ID “Technology” was here.
The first occurrence of ID “History” was here.
The “border” attribute is obsolete. Consider specifying “img { border: 0; }” in CSS instead.
The “button” role is unnecessary for element “button”.
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