Custom Widget Section in Blogger Homepage

CSS Section

* {
  box-sizing: border-box;
}
.coll {
  float: left;
  width: 33.33%;
  padding: 0px;
}
.coll-foter{
  float: left;
  width: 33.33%;
  padding: 20px;
}
.row12{
background:#e7edee;
margin-bottom: 25px;
box-shadow: 0 8px 10px 0 rgba(113, 113, 113, 0.22);
}
.row12:after {
  content: "";
  display: table;
  clear: both;
}

@media screen and (max-width:950px) {
  .coll {
    width: 100%;
  }
}
@media screen and (max-width:950px) {
  .coll-foter {
    width: 100%;
  }
}
.alert {
    padding: 20px;
    color: black;
}

.closebtn {
    margin-left: 15px;
    color:red;
    font-weight: bold;
    float: right;
    font-size: 25px;
    line-height: 20px;
    cursor: pointer;
    transition: 0.3s;
}

.closebtn:hover {
    color: black;
}

 

HTML Section

<div class='row12'>
  <div class='coll'></div>
  <div class='coll'></div>
  <div class='coll'></div>
</div>

<b:section class='Home-Notification' cond='data:view.isHomepage' id='Home-Notification' maxwidgets='10' showaddelement='yes'>  </b:section>