function validate() {
var themessage = "You are required to complete the following fields: ";
if (document.form.txtName.value=="") {
themessage = themessage + " -   Name";
}

if (document.form.txtEmail.value=="") {
themessage = themessage + " -  Email";
}
if (document.form.txtMessage.value=="") {
themessage = themessage + " -  Your Message";
}
//alert if fields are empty and cancel form submit
if (themessage == "You are required to complete the following fields: ") {
document.form.submit();
}
else {
alert(themessage);
return false;
   }
}