function countCharacters(textArea, counterField, maxLength){	
    if (textArea !=null && textArea.value != null) 
    {
        if (textArea.value.length > maxLength)
        {
            alert('Your message may not exceed ' +  maxLength + ' characters in length.');
            textArea.value = textArea.value.substring(0, maxLength);
        } 
        counterField.value = maxLength - textArea.value.length; 
    }
}