function validateFormOnSubmit(theForm) {
var reason = "";

  reason += validateFirstname(theForm.visitorfirst);
  reason += validateLastname(theForm.visitorlast);
  reason += validateEmail(theForm.visitormail);
  reason += validateEmpty(theForm.notes);
      
  if (reason != "") {
    alert("Fields marked with an (*) are required:\n" + reason);
    return false;
  }

  return true;
}



function validateEmpty(fld) {
    var error = "";
 
    if (fld.value.length == 0) {
        fld.style.background = 'Yellow'; 
       // error = "The required field has not been filled in.\n"
    } else {
        fld.style.background = 'White';
    }
    return error;  
}



function validateLastname(fld) {
    var error = "";
    var illegalChars = /\W/; // allow letters, numbers, and underscores
 
    if (fld.value == "") {
        fld.style.background = 'Yellow'; 
        error = "You didn't enter a Last Name.\n";
    } else if ((fld.value.length < 3) || (fld.value.length > 20)) {
        fld.style.background = 'Yellow'; 
        error = "The Last Name is the wrong length.\n";
    } else if (illegalChars.test(fld.value)) {
        fld.style.background = 'Yellow'; 
        error = "The Last name contains illegal characters.\n";
    } else {
        fld.style.background = 'White';
    }
    return error;
}


function validateFirstname(fld) {
    var error = "";
    var illegalChars = /\W/; // allow letters, numbers, and underscores
 
    if (fld.value == "") {
        fld.style.background = 'Yellow'; 
        error = "You didn't enter a First Name.\n";
    } else if ((fld.value.length < 3) || (fld.value.length > 20)) {
        fld.style.background = 'Yellow'; 
        error = "The First Name is the wrong length.\n";
    } else if (illegalChars.test(fld.value)) {
        fld.style.background = 'Yellow'; 
        error = "The First name contains illegal characters.\n";
    } else {
        fld.style.background = 'White';
    }
    return error;
}



function trim(s)
{
  return s.replace(/^\s+|\s+$/, '');
}

function validateEmail(fld) {
    var error="";
    var tfld = trim(fld.value);                        // value of field with whitespace trimmed off
    var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
    var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
   
    if (fld.value == "") {
        fld.style.background = 'Yellow';
        error = "You didn't enter an email address.\n";
    } else if (!emailFilter.test(tfld)) {              //test email for illegal characters
        fld.style.background = 'Yellow';
        error = "Please enter a valid email address.\n";
    } else if (fld.value.match(illegalChars)) {
        fld.style.background = 'Yellow';
        error = "The email address contains illegal characters.\n";
    } else {
        fld.style.background = 'White';
    }
    return error;
}