def _clean_html_a(name, value):
    """
    Clean the 'a' tag for an HTML field. This allows 'title',
    'target', and 'href's that point to http or https.
    """
    if name in ('title', 'target'):
        return True
    elif name == 'href':
        return value.startswith('http://') or value.startswith('https://')
    else:
        return False