The Indian stock markets today closed on a weaker note first time after three trading sessions. The Sensex at the Bombay stock Exchange declined 68 points at 20407. The broad based NSE Nifty went down by 13 points to close at 6145.The bourses saw 18 components ending in negative terrain. Some kept the market sentiments high.In the Broader market indices, the BSE Midcap index rose 64 points to close at 8334 while the BSE small cap index surged 118 points to close at 10556.The broad based NSE Nifty went down by 13 points to close at 6145.