<BDO></BDO> - BiDirectional Override

This tag is used to change text direction for multi-lingual documents (BDO stands for Bi-Directional Override). The DIR attribute is required. The reasons for its use are rather involved (and also beyond me), so if you want to learn how to use it, check out HTML 4.0 - The BDO Element

This tag must be closed at the end of the override by typing </BDO>.