How can i change background of a input with type of number when it's value is more than 100 or less than 1 . I want to use css.

Answer 1

You can't with css as far as I know ,but you can use js to do easily
var input=document.querySelectot("input[type=number]");
input.oninput=(e)=>{
If(e.target.value>100){
e.target.backgroundColor="red";
}
}

Answer 2

You have to use js as suggested
by Abhay

Css is use to design elements not to validate .
Html 5 have some built-in validation but it not fullfill your condition.