[solved] Please, help using jscall('history.back()');

Sorry, I edit because the question did not make sense:

The back_button with the code jscall('history.back()'); was located under the lateral layers to navigate between scenes. These layers are made visible only when you press the krpano button to hide the control bar. In this case the back_button lost its functionability.

Solution: Set zorder=99 to back_button.

Best Regards,
Fernando