code: function startTagInHead(p, token) {
      var tn = token.tagName;
  
      if (tn === $.HTML)
          startTagInBody(p, token);
  
      else if (tn === $.BASE || tn === $.BASEFONT || tn === $.BGSOUND ||
               tn === $.COMMAND || tn === $.LINK || tn === $.META) {
          p._appendElement(token, NS.HTML);
      }
  
      else if (tn === $.TITLE)
          p._switchToTextParsing(token, Tokenizer.MODE.RCDATA);
  
      //NOTE: here we assume that we always act as an interactive user agent with enabled scripting, so we parse
      //<noscript> as a rawtext.
      else if (tn === $.NOSCRIPT || tn === $.NOFRAMES || tn === $.STYLE)
          p._switchToTextParsing(token, Tokenizer.MODE.RAWTEXT);
  
      else if (tn === $.SCRIPT)
          p._switchToTextParsing(token, Tokenizer.MODE.SCRIPT_DATA);
  
      else if (tn === $.TEMPLATE) {
          p._insertTemplate(token, NS.HTML);
          p.activeFormattingElements.insertMarker();
          p.framesetOk = false;
          p.insertionMode = IN_TEMPLATE_MODE;
          p._pushTmplInsertionMode(IN_TEMPLATE_MODE);
      }
  
      else if (tn !== $.HEAD)
          tokenInHead(p, token);
  }
docs: 12.2.5.4.4 The "in head" insertion mode ------------------------------------------------------------------