div background color not setting all area

Question

I have a div containing 3 div inside it. My problem is when am setting background color to first div, the div inside first div is not applying the background.

My code is

Answer 1

This is your perfect answer for css.

.how_next {
    height:auto;
    background-color:#E9E9E9;
    padding:15px;
    font-size :16px;
    font-weight:bold;
    margin-top:10px;
    float:left;
    width:100%;
   }
.how_next_single {
    width:32%;
    float:left;
  }
.how_next_last {
    width:32%;
    float:right;
   }