यदक्षर पदभ्रष्टं मात्रा हीनन्तु यद्भवेत् ।
तत्सर्वं क्षम्यतां देव नारायण नमोऽस्तुते ॥

This is used to request the Lord to oversee any mistakes in chanting any puja or Slokas. Oh! nArAyaNa, I salute to you and I request you to pardon me for any mistakes I might have committed in uttering any letter, phrase and any syllables that I might have missed.

Word meanings:
यदक्षर = that letter;
पदभ्रष्टं = a slipped or missed word;
मात्रा = a unit of measurement; as far as; as little as, etc.;
तत्सर्वं = all that;
क्षम्यतां = let one or me or us be forgiven;
देव = Oh! god Oh! God!;
नारायण = O! Narayana;
नमोऽस्तुते = Salutations unto Thee;