var urls = [

  'https://twitter.com/jaffathecake',

  'https://twitter.com/paul_kinlan',

  'https://twitter.com/aerotwist',

  'https://twitter.com/addyosmani',

  'https://twitter.com/gauntface',

  'https://twitter.com/sw12'

];

var windows;

var width = 325;

var height = 1080;

​

document.querySelector('.prepare').onclick = function() {

  windows = urls.map(function(url, i) {

    return window.open('about:blank', 'win' + i, "menubar=no,toolbar=no,location=no,width=" + width + ",height=" + height + ',left=' + (width*i) + ',top=0');

  });

};

​

document.querySelector('.nav').onclick = function() {

  windows.forEach(function(win, i) {

    win.location.href = urls[i];

  });

};