css calc() fallback

// CSS calc() replacement
var myAddEventListener = (function () {
    "use strict";
    if (document.addEventListener) {
        return function (element, event, handler) {
            element.addEventListener(event, handler, false);
        };
    }
    return function (element, event, handler) {
        element.attachEvent('on' + event, handler);
    };
}());

function calcFailback() {
    "use strict";
    var d = document.createElement('div'),
        host = document.getElementsByTagName('body')[0],
        content = document.getElementById('content'),
        sidebar = document.getElementById('sidebar'),
        newWidth;

    function resize() {
        content.style.height = window.innerHeight - 40 + 'px';
        content.style.width = window.innerWidth - 300 + 'px';
        sidebar.style.height = window.innerHeight - 40 + 'px';
    }

    host.appendChild(d);

    d.style.visibility = 'hidden';
    d.style.width = "-webkit-calc(10px)";
    d.style.width = "-o-calc(10px)";
    d.style.width = "-moz-calc(10px)";
    d.style.width = "calc(10px)";

    newWidth = d.offsetWidth;

    if (newWidth !== 10) {

        resize();
        myAddEventListener(window, "resize", resize);

    }

    host.removeChild(d);
}

myAddEventListener(window, "load", calcFailback);