function isEmpty(s) { 
		return ((s == null) || (s.length == 0)) 
	}
	
	function isWhitespace (s) {   
		var i;
		var whitespace = " \t\n\r";
	    if (isEmpty(s)) 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;
	    }
	    return true;
	}
	
	function isValidEmail(s){   
		if (isEmpty(s)) return false;
		if (isWhitespace(s)) return false;
		var i = 1;
		var sLength = s.length;
		while ((i < sLength) && (s.charAt(i) != "@")) { i++ }
	  	if ((i >= sLength) || (s.charAt(i) != "@")) return false;
	    else i += 2;
	    while ((i < sLength) && (s.charAt(i) != "."))
	    { i++
	    }
	    if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
	    else return true;
	}