JSFiddle - React, Tailwind, and code Playground

HTML

<div style="position: absolute; width: 100%; height: 100%; background-color: #00FF00">
        <div style="position: relative; left: 300px; top: 45px; height: calc(100% - 55px); width: calc(100% - 300px); background-color: #FF0000;">
            <span style="position: absolute; right: 0; top: 50%;">TESTING THIS OUT</span>
        </div>
    </div>

CSS

/* Eric Meyer's Reset CSS v2.0 - http://cssreset.com */
html,body,div,span,applet,object,iframe,h1,h2,h3,h4,h5,h6,p,blockquote,pre,a,abbr,acronym,address,big,cite,code,del,dfn,em,img,ins,kbd,q,s,samp,small,strike,strong,sub,sup,tt,var,b,u,i,center,dl,dt,dd,ol,ul,li,fieldset,form,label,legend,table,caption,tbody,tfoot,thead,tr,th,td,article,aside,canvas,details,embed,figure,figcaption,footer,header,hgroup,menu,nav,output,ruby,section,summary,time,mark,audio,video{border:0;font-size:100%;font:inherit;vertical-align:baseline;margin:0;padding:0}article,aside,details,figcaption,figure,footer,header,hgroup,menu,nav,section{display:block}body{line-height:1}ol,ul{list-style:none}blockquote,q{quotes:none}blockquote:before,blockquote:after,q:before,q:after{content:none}table{border-collapse:collapse;border-spacing:0}