<div class="kutular">
<div class="kutu k1">
BURAYA NE LAZIMSA...
</div>

<div class="kutu k2">
BURAYA NE LAZIMSA...
</div>
</div>

.kutular {
max-width:1200px;
display:block;
margin:auto;
width:100%;
background:#ddd;
}
.kutu {
float:left;
width:50%;
display:inline-block;
background:#fff;
}
.k1 {
background: #f2952b;
}
.k2 {
background:#15d6ef;
}
@media screen and (max-width: 680px) {
  .kutu {
  width:100%;
  }
}