To your html question: it might happen that some features are not working correctly due to the different webview componentes on the Android and iOS OS. Also, on Android it might happen that the widget rendering differes from device model to model.
To your second questions - you'll need to detect the target image so that you display your augmentation. Then you can work e.g. with our snap-2-screen functionality.
about 3 years ago
i did an html drawable created by adobe edge , buttons animation and everything,and working great in chrom
the problem is that when the html.drawable shows ,some of the features dont work..
like blur and click on buttons to call or to email using location.href ="tel:13131313131" , it worked on chrom but not wikitude
another question , does the AR element appearing above the target makes the target hard to be detected ? cuzing the the AR element to bounce a couple of time untill it stop bouncing, sometimes it causes the app to close
how to make the scene goes on even if the target is out of vision ?