Important notice: following FAQ in changing effective viewportwidth is only working by direct page view and won't be working when used under iframe. That is the limitation of browsers that won't allow the child pages to control its effective size. So by usage of iframe the size control should be implemented by parent holder that includes the iframe with HTML5 client. Iframe loaded HTML5 client always uses the size reported by parent holder.
By default the HTML5 client reuses the default resolution of 1024 pixels in width where the height gets automatically computed by available screen height reported by browser excluding varying height of address bar, bottom bar etc, also purely computed by browser and can't be affected by the program engine. Doing so the browser controls minimal zoom level to fit the entire screen of your mobile device.
Since 1024 pixels setting doesn't always meet the needs of minimal width you can increase this value.
1. locate *\Clients\www\software\html5\settings.js > W.viewportwidth = "1024";
2. increase the value as example to W.viewportwidth = "1400";
PS: Additionally the program supports instead numeric value the string "device-width" by setting W.viewportwidth = "device-width"; In such case the program will try its best to recognize real device resolution and use its physical size rather than explicitely given numeric value. But that may work or not work at all depending on browser device constellation, therefore use it at your own risk where you may exclude some not widely used browsers from expected behaving!
Comparing to viewportwidth the variable viewportminwidth will increase effective resolution in width if given viewportwidth underflows the viewportminwidth, in such case the screen will overflow on right side so that to reach the most right edges you would need to scroll horizontally.
Let's imagine following scenario: W.viewportwidth = "1024"; and W.viewportminwidth= "1400";
In such case 1400 - 1024 = 376 pixels overflowing, also minimum visible area on screen will be 1024 pixels and 376 pixels will stay scrollable on right side, so that to reach these hidden 376 pixels you would need to scroll by horizontal panning (while holding one finger on screen move it immediately to right(or left) side).