The Sensex, last week, moved in our expected range of 15,550 to 14,650 till Friday when the index broke the lower end of the band. This now opens the possibility of the index drop to our earlier mentioned major support level of 13,800 (13,780 to be precise).While alternate bouts of buying and selling would lead to huge swings in the market, the short-term bias remains bearish as long as the index is below the 15,550-mark. Jittery global markets and a holiday-shortened trading week would add to the current nervousness.Last week, the index, after beginning on a dismal note, did extremely well to recoup its losses and gain over 400 points in intra-week trades. From an early low of 14,706, the Sensex surged to a high of 15,542 - a swing of 972 points. However, the index eventually dropped into the red and finished with a loss of 270 points at 14,868. This was the third straight weekly loss for the index.The current week could be a bit tricky one as the markets generally tend to reverse trend after three weeks. If not, the reversal may come after the seventh or the ninth week.While the support levels for the Sensex this week are placed at 14,500-14,380-14,265, the index will face resistance around 15,240-15,350-15,470.The Nifty swung in a near 300-point range, i.e., from a high of 4,530, the index tumbled to a low of 4,239 - an intra-week range of 291 points - before settling with a loss of 68 points at 4,333.The 4,520-4,530 levels would continue to be the major roadblocks for the Nifty and the bias will remain negative as long as the index trades below these levels. The Nifty, too, has broken its support level mentioned at 4,275-4,285. The index is now likely to test its lower levels of 4,030 to 3,960.This week, the index may face resistance around 4,445-4,480-4,515, while support on the downside is likely to be around 4,220-4,190-4,150.