JSFiddle - React, Tailwind, and code Playground

HTML

<div class="text-block important-block">
    test text for ie9
</div>

CSS

html {
    font-size: 100%;
}
body {
    font-size: 14px;
}
div:before {
    content: 'IE9-10-beforeText=9em';
    display: block;
    position: relative;
    font-size: 1.5em;
}
.text-block:before {
    font-size: 2em;
}
.important-block:before {
    font-size: 3em;
}