The error in your code might be because you adding an integer with string. Try following code:
<script type="text/javascript">
function Confirmcall() {
var empId = document.getElementById("txtEmpId").value;
var empName = document.getElementById("txtEmpName").value;
var empSalary = document.getElementById("txtSalary").value;
var empCity = document.getElementById("txtCity").value;
var msg = "Emp ID: " + empId + ",Emp Name: " + empName + ",Emp Salary: " + empSalary + ", Emp City: " + empCity;
return confirm(msg);
}
</script>
BTW, you could have used "improve question" in your question that you posted early today regarding the same problem.