<div>내용1</div>
<div>내용2</div>
<div>내용3</div>

* {
  margin: 0;
  padding: 0;
 }
div:nth-child(1) {
  background: red;
}
div:nth-child(2) {
  background: green;
}
div:nth-child(3) {
  background: blue;
}

$(document).ready(function() {
     $("div").eq(0).css({padding: 10, "text-align": "center"});
     $("div").css("width", function(index) {
         return index * 100 + 100; // 100,200,300
     });
 });