function isValidEmail(email, required) {
    if (required==undefined) {   // if not specified, assume it's required
        required=true;
    }
    if (email==null) {
        if (required) {
            return false;
        }
        return true;
    }
    if (email.length==0) {  
        if (required) {
            return false;
        }
        return true;
    }
    if (! allValidChars(email)) {  // check to make sure all characters are valid
        return false;
    }
    if (email.indexOf("@") < 1) { //  must contain @, and it must not be the first character
        return false;
    } else if (email.lastIndexOf(".") <= email.indexOf("@")) {  // last dot must be after the @
        return false;
    } else if (email.indexOf("@") == email.length) {  // @ must not be the last character
        return false;
    } else if (email.indexOf("..") >=0) { // two periods in a row is not valid
	return false;
    } else if (email.indexOf(".") == email.length) {  // . must not be the last character
	return false;
    }
    return true;
}

function allValidChars(email) {
  var parsed = true;
  var validchars = "abcdefghijklmnopqrstuvwxyz0123456789@.-_";
  for (var i=0; i < email.length; i++) {
    var letter = email.charAt(i).toLowerCase();
    if (validchars.indexOf(letter) != -1)
      continue;
    parsed = false;
    break;
  }
  return parsed;
}

function validate(field) {
var valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-"
var ok = "yes";
var temp;
for (var i=0; i<field.value.length; i++) {
temp = "" + field.value.substring(i, i+1);
if (valid.indexOf(temp) == "-1") ok = "no";
}
if (ok == "no") {
return false;
}
if (ok == "yes") {
return true;
}
}

function validate2(field) {
var valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ "
var ok = "yes";
var temp;
for (var i=0; i<field.value.length; i++) {
temp = "" + field.value.substring(i, i+1);
if (valid.indexOf(temp) == "-1") ok = "no";
}
if (ok == "no") {
return false;
}
if (ok == "yes") {
return true;
}
}

function validate3(field) {
var valid = "0123456789"
var ok = "yes";
var temp;
for (var i=0; i<field.value.length; i++) {
temp = "" + field.value.substring(i, i+1);
if (valid.indexOf(temp) == "-1") ok = "no";
}
if (ok == "no") {
return false;
}
if (ok == "yes") {
return true;
}
}

function validate4(field) {
var valid = "0123456789."
var ok = "yes";
var temp;
for (var i=0; i<field.value.length; i++) {
temp = "" + field.value.substring(i, i+1);
if (valid.indexOf(temp) == "-1") ok = "no";
}
if (ok == "no") {
return false;
}
if (ok == "yes") {
return true;
}
}

function validate5(field) {
var valid = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 "
var ok = "yes";
var temp;
for (var i=0; i<field.value.length; i++) {
temp = "" + field.value.substring(i, i+1);
if (valid.indexOf(temp) == "-1") ok = "no";
}
if (ok == "no") {
return false;
}
if (ok == "yes") {
return true;
}
}