Jim Cramer answers viewers' Twitter questions from the floor of the New York Stock Exchange. This week, he explains why retail investors were left out of the Alibaba initial public offering, and at what levels he'd be a buyer of the new issue now. After Barclays downgraded Walgreen to EQUAL WEIGHT from OVERWEIGHT, Cramer says the stock is not done going down and it's better to sell rather than buy here. He also says to take profits in World Wrestling Entertainment. On the flip side, he says stay with EMC Corp. despite uncertainty surrounding it. Make sure to tweet your questions @jimcramer every Monday using #CramerQ.