You want the app/page to be displayed in full size, rather than a scaled down version like most desktop pages are presented on the iPhone. You also want to prevent the user to scale the viewport with a two-finger pinch gesture.
You can set up a meta-tag that prevents the iPhone from letting the user scale the content with two fingers.
The solution is simple. Just insert this meta-tag into the header of your HTML document:
<meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1.0,user-scalable=no">
This will set the safari browser to ignore scaling attempts from the page visitor.