Speed up websites

Image part

Compression tools to reduce the file size of images

• TinyPNG – Compress WebP, PNG and JPEG images intelligently

JavaScript part

Compression tools to reduce the file size of javascript

• Minify Javascript Online / Online JavaScript Packer
• Sublime Text 2 YUI-Compressor plugin
• $ PhpStorm IDE Minifying JavaScript

Using CDN (Content Delivery Network)

• Google Hosted Libraries - Developer's Guide - Make the Web Faster — Google Developers
• Microsoft Ajax Content Delivery Network - ASP.NET Ajax Library
• cdnjs.com - the missing cdn for javascript and css & 中文版: cdnjs.com - 遺失的CDN的JavaScript和CSS [Last visited: 2014-09-10]
• UNPKG [Last visited: 2018-10-18]

//If the javascript library hosted at CDN was failed to connect, it will switch to local javascript file automatically.

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js" type="text/javascript"></script>
<script>!window.jQuery && document.write('<script src="local-js-path/jquery-1.12.4.min.js"><\/script>');</script>

<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.9.2/jquery-ui.min.js" type="text/javascript"></script>
<script>!window.jQuery.ui && document.write('<script src="local-js-path/jquery-ui-effects.custom-1.9.2.min.js"><\/script>');</script>