Force page zoom at 100% with JS

You can set zoom property on page load

document.body.style.zoom = 1.0

But, zoom is not a standard property for all browsers, I recommend using transform instead.

var scale="scale(1)";
document.body.style.webkitTransform =  scale;    // Chrome, Opera, Safari
 document.body.style.msTransform =   scale;       // IE 9
 document.body.style.transform = scale;     // General

http://jsfiddle.net/5RzJ8/