Validation JavaScript in Button

script language="javascript"
function validation() {
if(document.getElementById('txtDomainName').value == ''){
alert("Plase Enter value for Dname Name");
document.frmAddPaymentMethod.focus();
return false;
}
if(document.getElementById('txtCurrencyCode').value == ''){
alert("Plase Enter value for Currency Code");
document.frmAddPaymentMethod.txtCurrencyCode.focus();
return false;
}
if(document.getElementById('txtCurrencySymbol').value == ''){
alert("Plase Enter value for Currency Symbol");
document.frmAddPaymentMethod.txtCurrencySymbol.focus();
return false;
}
if(document.getElementById('txtBaseConversionRate').value == ''){
alert("Plase Enter value for Base Conversion Rate");
document.frmAddPaymentMethod.txtBaseConversionRate.focus();
return false;
}
if(document.getElementById('ddlCountry').value == ''){
alert("Plase Select Country");
document.frmAddPaymentMethod.ddlCountry.focus();
return false;
}

if(document.getElementById('ddlLanguage').value == ''){
alert("Please Select Language");
document.frmAddPaymentMethod.ddlLanguage.focus();
return false;
}
return true;
}
/script

*************************************************************************************

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

btnAdd.Attributes.Add("onclick", "return validation();")

If IsPostBack = False Then


End if
End sub