Now, look at your web page. How many pixels are between the items on your navbar? If you answer less than 40, then you’re effectively asking your visitor to play Russian roulette: their 40-80 pixel finger isn’t going to hit your 20 pixel link effectively.
When you use iPhone specific styles, it improves accessibility for someone working on a high-density mobile device. My rule of thumb is to double important elements: bumping a font-size from 18px to 36px, for example. You’ll want to focus both on interactive elements (such as <a> and <input>) and navigational indicators (such as section titles and bread crumb trails).