// isEmail (STRING s [, BOOLEAN emptyOK])
// whitespace characters
var whitespace = " \t\n\r";

//
// Email address must be of form a@b.c ... in other words:
// * there must be at least one character before the @
// * there must be at least one character before and after the .
// * the characters @ and . are both required
function isValidEmail(s)
{
    if (isEmpty(s)) return false;
   
    // is s whitespace?
    if (isWhitespace(s)) return false;
        
    // there must be >= 1 character before @, so we
    // start looking at character position 1
    // (i.e. second character)
    var i = 1;
    var sLength = s.length;

    // look for @
    while ((i < sLength) && (s.charAt(i) != "@"))
    { i++
    }

    if ((i >= sLength) || (s.charAt(i) != "@")) return false;
    else i += 2;

    // look for .
    while ((i < sLength) && (s.charAt(i) != "."))
    { i++
    }

    // there must be at least one character after the .
    if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
    else return true;
}

// Check whether string s is empty.
function isEmpty(s)
{
    return ((s == null) || (s.length == 0))
}

// Returns true if string s is empty or
// whitespace characters only.
function isWhitespace(s)
{
    var i;

    // Is s empty?
    if (isEmpty(s)) return true;

    // Search through string's characters one by one
    // until we find a non-whitespace character.
    // When we do, return false; if we don't, return true.
    for (i = 0; i < s.length; i++)
    {
        // Check that current character isn't whitespace.
        var c = s.charAt(i);

        if (whitespace.indexOf(c) == -1) return false;
    }
    // All characters are whitespace.
    return true;
}

function checkForm() 
{
/*    z=0;
    celements=document.getElementsByName('lid');
        for (c=0;c<celements.length;c++){
        if (celements[c].checked){
            z=z+1;
            }
        }
    if (z<1){
    alert("Please select at least one list.");
        return false;
    }
*/
    if (!isValidEmail(document.subscribeForm.elements['Email Address'].value)) {
    document.subscribeForm.elements['Email Address'].style.backgroundColor='yellow';
        alert("Please enter a valid Email Address. e.g. name@host.com");
        document.subscribeForm.elements['Email Address'].focus();
        return false;
    }
}