function isValidEmail(address) {
  if (address.indexOf('@') < 3) return false;
  var name = address.substring(0, address.indexOf('@'));
  var domain = address.substring(address.indexOf('@') + 1);
  if (name.indexOf('(') != -1 || name.indexOf(')') != -1 || name.indexOf('<') != -1 || name.indexOf('>') != -1 || name.indexOf(',') != -1 || name.indexOf(';') != -1 || name.indexOf(':') != -1 || name.indexOf('\\') != -1 || name.indexOf('"') != -1 || name.indexOf('[') != -1 || name.indexOf(']') != -1 || name.indexOf(' ') != -1) return false;
  if (domain.indexOf('(') != -1 || domain.indexOf(')') != -1 || domain.indexOf('<') != -1 || domain.indexOf('>') != -1 || domain.indexOf(',') != -1 || domain.indexOf(';') != -1 || domain.indexOf(':') != -1 || domain.indexOf('\\') != -1 || domain.indexOf('"') != -1 || domain.indexOf('[') != -1 || domain.indexOf(']') != -1 || domain.indexOf(' ') != -1) return false;
  return true;
}

function trimWhitespace(string) {
  var newString  = '';
  var substring  = '';
  beginningFound = false;

  // copy characters over to a new string
  // retain whitespace characters if they are between other characters
  for (var i = 0; i < string.length; i++) {

  // copy non-whitespace characters
  if (string.charAt(i) != ' ' && string.charCodeAt(i) != 9) {

    // if the temporary string contains some whitespace characters, copy them first
    if (substring != '') {
      newString += substring;
      substring = '';
    }
    newString += string.charAt(i);
    if (beginningFound == false) beginningFound = true;
  }

  // hold whitespace characters in a temporary string if they follow a non-whitespace character
  else if (beginningFound == true) substring += string.charAt(i);
  }
  return newString;
}

function checkFields() {
  var errstr = "";

  if (trimWhitespace(document.inputform.firstname.value).length == 0) {
    errstr += "- First Name\r\n";
  }
  if (trimWhitespace(document.inputform.lastname.value).length == 0) {
    errstr += "- Last Name\r\n";
  }
  if (!isValidEmail(document.inputform.email.value)) {
    errstr += "- Valid email address\r\n";
  }

   if (errstr.length == 0) {
     document.inputform.submit();
     return true;
   } else {
     alert("Please enter information in the following fields:\r\n" + errstr);
     return false;
   }
 }