CSS for responsive website

[Afflospark]

Hello,
First, I tell you that responsive web design is not a program or javascript. And it uses on HTML or CSS.
You can also use bootstrap with these languages to make your website better-looking and more user friendly.
Hope this will help you.
Thanks

[Afflospark]

After reading all the above comments, I was wondering, Why do you guys even need to create a new one when you copy it from available ones.
I was using WordPress for years. But now I needed a custom website with just 3 pages (Home, About-Us, ContactUs), I tried to create a new CSS file which can provide me responsive layout with mobile as well as desktop. But couldn't create. Then I just checked my WordPress website and copied its style.css (How to open Wordpress CSS file) and pasted it to my new website.
Actually, it worked well, and I'm still using it.

You can also try this method if you are lazy to write your own CSS.
Thanks

[jason23160]

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. It is called responsive web design when you use CSS and HTML to resize, hide, shrink, enlarge, or move the content to make it look good on any screen.