JavsScript Invert all colors on a webpage including images and CSS

(function() {
    var css = 'html {-webkit-filter: invert(100%); -moz-filter: invert(100%); -o-filter: invert(100%); -ms-filter: invert(100%);}'
      , head = document.getElementsByTagName('head')[0]
      , style = document.createElement('style');
    if (!window.counter) {
        window.counter = 1;
    } else {
        window.counter++;
        if (window.counter % 2 == 0) {
            css = 'html {-webkit-filter: invert(0%); -moz-filter: invert(0%); -o-filter: invert(0%); -ms-filter: invert(0%);}'
        }
    }
    style.type = 'text/css';
    if (style.styleSheet) {
        style.styleSheet.cssText = css;
    } else {
        style.appendChild(document.createTextNode(css));
    }
    head.appendChild(style);
})();