Hola Mundo JavaScript
Código
<!DOCTYPE html PUBLIC «-//W3C//DTD XHTML 1.0 Transitional//EN» «http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd»>
<html xmlns=»http://www.w3.org/1999/xhtml»>
<head>
<meta http-equiv=»Content-Type» content=»text/html; charset=utf-8″ />
<title>Documento sin título</title>
<script language=»javascript»>
alert(«HOLA MUNDO»)
</script>
</head>
<body>
</body>
</html>