function validateEmpty(fld) {
  var error = "";

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




function validateUsername(fld) {
  var error = "";
  var illegalChars = /\W/; // allow letters, numbers, and underscores

  if (fld.value == "") {
    fld.style.background = 'Yellow';
    error = "You didn't enter a username.\n";
  } else if ((fld.value.length < 5) || (fld.value.length > 15)) {
    fld.style.background = 'Yellow';
    error = "The username is the wrong length.\n";
  } else if (illegalChars.test(fld.value)) {
    fld.style.background = 'Yellow';
    error = "The username contains illegal characters.\n";
  } else {
    fld.style.background = 'White';
  }
  return error;
}




function validatePassword(fld) {
  var error = "";
  var illegalChars = /[\W_]/; // allow only letters and numbers

  if (fld.value == "") {
    fld.style.background = 'Yellow';
    error = "You didn't enter a password.\n";
  } else if ((fld.value.length < 7) || (fld.value.length > 15)) {
    error = "The password is the wrong length. \n";
    fld.style.background = 'Yellow';
  } else if (illegalChars.test(fld.value)) {
    error = "The password contains illegal characters.\n";
    fld.style.background = 'Yellow';
  } else if (!((fld.value.search(/(a-z)+/)) && (fld.value.search(/(0-9)+/)))) {
    error = "The password must contain at least one numeral.\n";
    fld.style.background = 'Yellow';
  } 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;
}


function validatePhone(fld) {
  var error = "";
  var stripped = fld.value.replace(/[\(\)\.\-\ ]/g, '');

   if (fld.value == "") {
    error = "You didn't enter a phone number.\n";
    fld.style.background = 'Yellow';
  } else if (isNaN(parseInt(stripped))) {
    error = "The phone number contains illegal characters.\n";
    fld.style.background = 'Yellow';
  } else if (!(stripped.length == 10)) {
    error = "The phone number is the wrong length. Make sure you included an area code.\n";
    fld.style.background = 'Yellow';
  } else {
    fld.style.background = 'White';
  }
  return error;
}



function validateCheck(fld) {
  var error = "";
  var tosagree = 1;

  if ( !fld.checked ) {
    error = "You must click to agree to the terms of service.\n";
    tosagree = document.getElementById("tosagree");
    tosagree.style.background = 'Yellow';
  }
  else {
    tosagree = document.getElementById("tosagree");
    tosagree.style.background = 'White';
  }
  return error;
}