Why it shows me this eror

Question

It show cannot set style of null

https://code.sololearn.com/WoNsE17D7kG8/?ref=app

Answer 1

Codes on JS tag are placed on HTML head tag and hence the code runs before dom loads.
Place your script on body tag or use:

window.onload = function(){
//Your code here
}

Use the search bar next time. This question is faq:
https://www.sololearn.com/Discuss?ordering=MostRecent&query=cannot%20null

Answer 2

Thanks Kevin ★ .Solved