The below code snippet explains how to check whether the HTML SELECT Dropdown item other than the default item is selected or not using jQuery
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
 <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <title></title>
    <script type = "text/javascript">
        $("#demo").live("click", function () {
            if ($("#ddl")[0].selectedIndex <= 0) {
                alert("Please select");
            }
        });
    </script>
</head>
<body>
    <form id="form1">
    <select id="ddl">
        <option value="0">Please select</option>
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3">3</option>
    </select>
    <input type = "button" id = "demo" value = "Demo" />
    </form>
</body>
</html>
 
Explanation:
In the above code snippet click event handler has been attached to the HTML input button with ID demo. When the button is clicked we check whether the selectedIndex of the HTML SELECT Dropdown is 0 or -1. The selectedIndex is -1 when no action has been taken on the HTML SELECT Dropdown. Once an option is selected the selectedIndex is set to the ZERO BASED INDEX of that option. Since the 0th Option is generally the default option I have checked for both 0 and -1 values.
Demo: