// Count number of chars left in the field
function gbCountChars(textareaID, outputID, max_chars) {
    var maxChars = max_chars;
    var textarea = document.getElementById(textareaID);
    var output = document.getElementById(outputID);
    if (textarea.value.length > maxChars) output.innerHTML = "Sorry. Your message is too long.";
    else output.innerHTML = "You have "+(maxChars - textarea.value.length)+" characters left.";
}

// Change the style of an input field to invalid
function gbMakeInvalid(labelID, fieldID) {
    var label = document.getElementById(labelID);
    label.className = "error";
    var field = document.getElementById(fieldID);
    field.className = "error";
}