Up until April 2019 UPDD Gestures could not be used to control touch-enabled web pages.
The problem is that OS X doesn't pass its system-level touch events to web browsers as HTML5 / javascript touches. So while these pages will work with an iPad (and similar) they do not work in OS X, even when using Apple’s magic trackpad.
However we have now created browser extensions for Firefox and Chrome that does cater for multi-touch input as described here.