grid without bootstrap

by padma rubhan

HTML

<div> I am using style disple flex bcoz I dont know how to use bootstap here(On this site)</div>
<div class="col-lg-12 col-md-12 col-sm-12 ">
    <div class="col-lg-3 col-md-3 col-sm-3 left" style="max-height: 100px;">some text</div>
    <div class="col-lg-6 col-md-6 col-sm-6 center" id="displayPost" style="max-height: 200px;overflow: auto !important;">post display using ajax<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br></div>
    <div class="col-lg-3 col-md-3 col-sm-3 right" style="max-height: 100px;overflow: auto !important;">//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br>//some text<br></div>
 </div>

CSS

.left{
    width: 100px;
}
.center{
  width: 300px;
  position: absolute;
  right: 300px
}
.right{
  width: 300px.;
  position: absolute;
  right: 0;
  top: 50px
}