JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class="container">
        <div class="sidebar">
            <div class="test1"></div>
            <div class="test2"></div>
        </div>
        <div class="mainpage"></div> 
    </div>
    <div class="footer"></div>
</body>

CSS

.container{
  /*width: 1654px;*/
  width: 100%;
  background-color: #f0f0f0;
  margin: 0 auto;
}
.sidebar{
	position: sticky;
	bottom: 10px;
  /* top: 10px; */
  width: 30%;
  margin: 5px;
  background-color: teal;
  height: 1000px;
  display: inline-block;
}
.mainpage{
  width: 67%;
  margin: 5px;
  margin-left: 0px; 
  background-color: steelblue;
  height: 2000px;
  display: inline-block;
}
.footer{
  height: 500px;
  width: 100%;
  margin: 0 auto;
  margin-top: 10px;
  background-color: purple
}
.test1{
  background-color: red;
  position: relative;
  left: 0;
  right: 0;
  top: 0;
  height: 200px;
}
.test2{
  background-color: red;
  position: relative;
  left: 0;
  right: 0;
  bottom: 0;
  height: 200px;
}