Masteringchemistry.com W3C HTML Markup Validation
HTML markup errors and warnings
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Errors:
A “meta” element with an “http-equiv” attribute whose value is “X-UA-Compatible” must have a “content” attribute with the value “IE=edge”.
Bad value “https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,400,300,600,700,800|Playfair+Display:400,700,900,400italic,700italic” for attribute “href” on element “link”: Illegal character in query: “|” is not allowed.
Bad value “educators/results/results-library.php?product[]=Mastering%20Chemistry&hpd” for attribute “href” on element “a”: Illegal character in query: “[” is not allowed.
Bad value “ext” for attribute “rel” on element “a”: The string “ext” is not a registered keyword.
Warnings:
The “banner” role is unnecessary for element “header”.
The “navigation” role is unnecessary for element “nav”.
Document uses the Unicode Private Use Area(s), which should not be used in publicly exchanged documents. (Charmod C073)
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).
Section lacks heading. Consider using “h2”-“h6” elements to add identifying headings to all sections.
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