RWD makes your web page look good on all devices. Web pages can be viewed using many different devices: desktops, tablets, and phones. Your web page should look good, and be easy to use, regardless of the device. Web pages should not leave out information to fit smaller devices, but rather adapt its content to fit any device.
Your valuable customers. It's pretty simple: the faster the speed of your website, the happier your visitors will be. Optimizing page load time leads to noticable improvements in customer experience, conversion rates, and ultimately, your sales revenue.
A recent HubSpot study finds that
Use CDN to improve your website performance globally, including China.
YouTube is better than thousand words.