JSFiddle - React, Tailwind, and code Playground

HTML

<div id="containerBox" class="containerBox">
    <div id="catBox" class="catBox">
        <ul id="categories" class="cat_menu"></ul>
    </div>
    <div id="pluginBox" class="pluginBox">
        <table id="pluginTable" class="plugin_table">
            
        </table>
    </div>
</div>

CSS

.containerBox {
    border:1px solid red;
    margin: auto;
}

.containerBox:after,
.containerBox::after {
  clear: both;
  content: "";
  display: table;
}
.catBox {
    float: left;
    height: 750px;
    width: 20%;
    overflow: auto;
    margin: 0;
    border: solid black 1px;
}
.pluginBox {
    float: left;
    margin-left: 25px;
    height: 750px;
    width: 75%;
    overflow: auto;
    border: solid black 1px;
}