Improved Counterspell [General]
You understand the nuances of magic to such an extent that you can counter your opponenet's spells with great efficiency.
Benefit: When counterspelling, you may use a spell of the same school that is one or more spell levels higher then the target spell.
Normal: Without this feat, you may counter a spell only with the same spell or with a spell specifically designated as countering the target spell.
Source: Player's Handbook