A form with an error should be considered to be dirty and prompt if the user leaves the page.

If a form with a textarea has been submitted but is returned with errors, the form should be considered dirty (i.e. not saved).
This will prevent people losing forms with large amounts of unsaved text if the accidentally navigate away or close the page.

Integration tests will need to be considered when making this change as if the dirty form warning appears it needs to be handled in a specific way. See: http://code.google.com/p/selenium/issues/detail?id=27

Code required for isDirty::isElementDirty

if ($form.has(".error, .errMsg, .errorMessage, .errLabel, .ajaxerror").length > 0 || $form.prev(".error").length > 0) {
    // Treat the form as dirty if it contains errors -- the form data is unlikely to be saved.
    return true;
}