Quote “"” in attribute name. Probable cause: Matching quote missing somewhere earlier.

Quote characters used for attributes can use either single quotes (') or double quotes ("), and they must be properly matched, for example:

<p class="news">...</p>

A common cause for this issue is forgetting to use the equal sign (=), so the HTML parser wrongly believes the quote forms part of the attribute name, for example:

<p class "news">this is wrong</p>