.db-2col { border: 1px solid red; overflow: hidden; }
.db-2col .db-col-first { float: left; width: 50%; }
.db-2col .db-col-last { float: left; width: 50%; }

<div class="db-2col">
  <div class="db-col-first">
  first column
  </div>

  <div class="db-col-last">
  second column
  </div>
</div>


.db-3col { border: 1px solid red; overflow: hidden; }
.db-3col .db-col-first { float: left; width: 25%; }
.db-3col .db-col { float: left; width: 50%; }
.db-3col .db-col-last { float: left; width: 25%; }

<div class="db-3col">
  <div class="db-col-first">
    first column
  </div>

  <div class="db-col">
    middle column
  </div>

  <div class="db3-col-last">
    last column
  </div>
</div>