The BSE Sensex fell by over 76 points in opening trade today as funds and retail investors booked gains recorded in the previous three sessions despite a firming trend on other Asian bourses. The 30-share index which had gained nearly 840 points in the previous three sessions, fell by 76.32 points, to 16,770.51 in opening trade today.In a similar fashion, the wide-based National Stock Exchange Nifty shed over 25 points, to around 5,025.