Errors:
Almost standards mode doctype. Expected “<!DOCTYPE html>”.
Bad value “https://www.w3.org/1999/xhtml” for the attribute “xmlns” (only “http://www.w3.org/1999/xhtml” permitted here).
No space between attributes.
A slash was not immediately followed by “>”.
Saw “"” when expecting an attribute name. Probable cause: “=” missing immediately before.
Bad value “” for attribute “href” on element “link”: Must be non-empty.
Attribute “https:” not allowed on element “link” at this point.
Attribute “www.mathnook.com” not allowed on element “link” at this point.
Attribute “"” not allowed on element “link” at this point.
Internal encoding declaration “windows-1252” disagrees with the actual encoding of the document (“utf-8”).
Element “object” is missing one or more of the following attributes: “data”, “type”.
The “classid” attribute on the “object” element is obsolete. Use the “data” and “type” attributes to invoke plugins. To set a parameter with the name “classid”, use the “param” element.
An “img” element must have an “alt” attribute, except under certain conditions. For details, consult guidance on providing text alternatives for images.
Element “script” must not have attribute “async” unless attribute “src” is also specified.
Element “style” not allowed as child of element “div” in this context. (Suppressing further errors from this subtree.)
Warnings:
Attribute “xmlns” is not serializable as XML 1.0.
Attribute “https:” is not serializable as XML 1.0.
Attribute “"” is not serializable as XML 1.0.
This document appears to be written in English. Consider adding “lang="en"” (or variant) to the “html” start tag.
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