A fix for iPhone viewport scale bug

source code
var viewportmeta = document.querySelector && document.querySelector('meta[name="viewport"]'),
ua = navigator.userAgent,
gestureStart = function(){
    viewportmeta.content = "width=device-width, minimum-scale=0.25, maximum-scale=1.6";
},
scaleFix = function(){
  if (viewportmeta && /iPhone|iPad/.test(ua) && !/Opera Mini/.test(ua)) {
    viewportmeta.content = "width=device-width, minimum-scale=1.0, maximum-scale=1.0";
    document.addEventListener("gesturestart", gestureStart, false);
  }
};
scaleFix();​

source: http://www.blog.highub.com/mobile-2/a-fix-for-iphone-viewport-scale-bug/