I want to learn web development from basic i have a basic knowledge of HTML,CSS and JS what can i do?
Do you have a computer? Does that run Windows or Mac OS: then the easiest thing is to install something like https://www.mamp.info/. If your computer runs Linux, then install locally Apache, MySQL, PHP and start playing around. There are dozens of good guides for you to get started: use google creatively, think about joining a local user group (head to meetup.com and see what’s available in your area). Check community college classes, online classes on coursera or edx and other online teaching environments…
This should get you started. Have fun!
Don’t forget all the free courses you can get from https://www.codecademy.com/learn or https://www.edx.org/. I have taken web development courses on both those sites and recommend them. And the price is right: free.