codice:
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Pagina senza titolo</title>
<script type="text/javascript">
var bCtrl = false;

document.onkeydown = function (oEvent) {
	bCtrl = (oEvent || window.event).ctrlKey;
}

document.onkeyup = function () {
	bCtrl = false;
}

function miaFunzione () {
	alert(bCtrl); // true o false a seconda che l'utente stia tenendo premuto il tasto control o meno
}
</script>
</head>

<body>


<span onclick="miaFunzione();" style="cursor:pointer;text-decoration:underline;color:#0000ff;">Clicca qui</span></p>
</body>

</html>