Changing Aspects of StairDesigner's Interface Display
У вашего броузера проблема в совместимости с HTML5
This video will look at how to change common display options in StairDesigner. This includes changing the language, the units from metric or imperial, and the background colour of the 3D view.
Find out more about this and other StairDesigner features here: https://wooddesigner.org/support/stairdesigner-videos/interface/