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.");
}
}