HtmlUnknownElement
sealed class HtmlUnknownElement : HtmlElement, IHtmlUnknownElement, IHtmlElement, IElement, INode, IEventTarget, IMarkupFormattable, IParentNode, IChildNode, INonDocumentTypeChildNode, IGlobalEventHandlers
The class for an unknown HTML element.
public HtmlUnknownElement(Document owner, string localName, string prefix = null, NodeFlags flags = 0)