<html>
<head>
    <title>Mouse Buttons Test Page</title>
    <style type="text/css">
        #input {
            width: 200px;
            height: 200px;
            border: 1px solid red;
        }
    </style>
    <script type="text/javascript">

        window.onload = function() {
            var input = document.getElementById('input'),
                check = document.getElementById('check');

            input.addEventListener('mousedown', function(e) {
                check.innerHTML = e.button;
            });
        };

    </script>
</head>
<body>
<div id="input" />
<div id="check" />

</body>

</html>
