Invert color of all elements

invert.js

javascript: (
function () { 
//based on https://stackoverflow.com/questions/4766201/javascript-invert-color-on-all-elements-of-a-page
// the css we are going to inject
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');

// a hack, so you can "invert back" clicking the bookmarklet again
if (!window.counter) { window.counter = 1;} else  { window.counter ++;
if (window.counter % 2 == 0) { var 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));
}

//injecting the css to the head
head.appendChild(style);
}());