<!DOCTYPE html>
<html>
<head>
<style>
h1 {
color: yellow;
text-shadow: -1px 0 black, 0 1px black, 1px 0 black, 0 -1px black;
}
</style>
</head>
<body>
<h1>围绕文本的边框！</h1>
</body>
</html>