Username:<br />
<select name="slt_usernames" id="slt_usernames" multiple>
 <option value="1001">Siva</option>
 <option value="1002">Raja</option>
 <option value="1003">Roja</option>
 <option value="1004">Lakshanya</option>
 <option value="1005">Vidhyaa</option>
</select>
<br /><br />
<button onclick="javascript:validate();">Validate</button>

function validate(){
    var n = document.getElementById("slt_usernames").options.length;
    for (var i = 0;i < n; i++){
        if (document.getElementById("slt_usernames").options[i].selected === true)
            alert(document.getElementById("slt_usernames").options[i].value+" is selected.");
        else
            alert(document.getElementById("slt_usernames").options[i].value+" is not selected.");
    }
}