Fixing website styles with GreaseMonkey / TamperMonkey

There may be a case that you visit a website with bad-looking design, but you can’t change it. You do not own that website.
Take a look at this www.runscope.com which provide API testing service. Here is the screenshot in Chrome 39 under Windows 7 64-bit. Their default font is “Source Sans Pro” which somehow look bad:

Then with just a little effort: install TamperMonkey then add the script below, the problem is solved.

// ==UserScript==
// @name         Change font style of RunScope
// @namespace    http://diophung.com/
// @version      0.1
// @description  Replace RunScope ugly font
// @author       Dio Phung
// @match        https://www.runscope.com/*
// @grant        none
// ==/UserScript==

//Change the ugly font of RunScope
document.body.style.fontFamily = "PT Sans";

Here is how the new www.runscope.com looks like: the font is much easier to read.