Change the whole pages' font into something fancy

changeBrowserFontIranSansDroidSans.user.js

// ==UserScript==
// @name        MeFirefox
// @namespace   MyDebian
// @description Change All fonts across FF
// @include     http*
// @version     1
// @grant       none
// ==/UserScript==

var css = "h1, h2, h3, h4, h5, h6, #firstHeading,.pod_body, #lst-ib, td, body, html, p, tr, div, a, main-body, textarea {font-family: 'Futura BT', sans-serif !important;} strong, b {font-weight: 900;}",
    head = document.head || document.getElementByTagName("head")[0],
    style = document.createElement("style");
style.type = "text/css";
if (style.styleSheet){
  style.stylesheet.cssText = css;
} else {
  style.appendChild(document.createTextNode(css));
}
head.appendChild(style);