<!DOCTYPE HTML>
<html>
    <head>
        <style>
        #testDiv {
            height: 100px;
            border: 1rem solid blue;
            background-color: rgba(0, 255, 0, 255);
        }
        </style>
    </head>
    <body>
        <div id="testDiv">This is a test</div>
    </body>
</html>