Mathandmultimedia.com W3C HTML Markup Validation
HTML markup errors and warnings
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Warnings:
Consider avoiding viewport values that prevent users from resizing documents.
The “navigation” role is unnecessary for element “nav”.
The “banner” role is unnecessary for element “header”.
The “language” attribute on the “script” element is obsolete. You can safely omit it.
Errors:
Bad value “https://api.w.org/” for attribute “rel” on element “link”: The string “https://api.w.org/” is not a registered keyword.
Bad value “http://rcm-na.amazon-adsystem.com/e/cm?t=mathemandmult-20&o=1&p=12&l=st1&mode=books&search=mathematics, algebra, geometry&fc1=000000<1=_blank&lc1=3366FF&bg1=FFFFFF&f=ifr” for attribute “src” on element “iframe”: Illegal character in query: space is not allowed.
Attribute “border” not allowed on element “iframe” at this point.
The “marginwidth” attribute on the “iframe” element is obsolete. Use CSS instead.
The “marginheight” attribute on the “iframe” element is obsolete. Use CSS instead.
The “frameborder” attribute on the “iframe” element is obsolete. Use CSS instead.
The “scrolling” attribute on the “iframe” element is obsolete. Use CSS instead.
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