Are online certificate of any value in the job market? If yes which website are given more value?

Answer 1

I guess yes. Some websites provide valuable certificates which you can use in job. But rather I would say gain knowledge not certificates.
Sites like Udemy and Coursera might be providing valuable certificates

Answer 2

If you want certification in web development go for w3school and for others like iot, machine learning you can go for coursera or udemy