This usually means that the user mixed up our lowercase/uppercase naming convention; see https://github.com/facebook/react/pull/3429#issuecomment-85166440.

We could add a message like

> Warning: The tag <commentBox> is unrecognized in this browser. If you meant to render a React component, start its name with an uppercase letter.

We'd check this only once per tag and only in development mode.

render() {
          return <div style={1} />;
        }
      }
      expect(function() {
        ReactDOM.render(<Animal />, container);
      }).toThrowError(
        'The `style` prop expects a mapping from style properties to values, ' +
          "not a string. For example, style={{marginRight: spacing + 'em'}} " +
          'when using JSX.\n\nThis DOM node was rendered by `Animal`.',
      );
    });
    it('should properly escape text content and attributes values', () => {
      expect(
        ReactDOMServer.renderToStaticMarkup(
          React.DOM.div(
            {
              title: '\'"<>&',
              style: {
                textAlign: '\'"<>&',
              },
            },
            '\'"<>&',
          ),
        ),
      ).toBe(
        '<div title="&#x27;&quot;&lt;&gt;&amp;" style="text-align:&#x27;&quot;&lt;&gt;&amp;;">' +