$r['thead@background'] = new HTMLPurifier_AttrTransform_Background();
$r['tfoot@background'] = new HTMLPurifier_AttrTransform_Background();
$r['tbody@background'] = new HTMLPurifier_AttrTransform_Background();
$r['thead@background'] = new HTMLPurifier_AttrTransform_Background();
$r['tfoot@background'] = new HTMLPurifier_AttrTransform_Background();
$r['tbody@background'] = new HTMLPurifier_AttrTransform_Background();