<!DOCTYPE html>
<style>
.a + span::before { content: "PA" }
.b + ::before { content: "SS" }
</style>
<p>You should see the word PASS below.</p>
<span id="t1"></span><span></span><span id="t2"></span><span></span>
<script>
document.body.offsetTop;
t1.className = "a";
t2.className = "b";
</script>