// 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 (!isValidEmail(document.subscribeForm.elements['Email Address'].value)) {
document.subscribeForm.elements['Email Address'].style.backgroundColor='yellow';
alert("Please enter a valid Email Address. (name@host.com)");
document.subscribeForm.elements['Email Address'].focus();
return false;
}
}