They used part of her nomination speech at the convention:

How are you going to be better off if our opponent adds a massive tax burden to the American economy?[…]The Democratic nominee for President supports plans to raise income taxes, and raise payroll taxes, and raise investment income taxes. How are you going to be better off if our opponent adds a massive tax burden to the American economy?

Obama says that he’ll cut taxes for the middle class but since he said he’ll allow the Bush tax cuts to expire, we know that our taxes will be raised. It’s wasn’t just the rich who received a tax cut. Now is not the time to burden the economy with taxes, especially corporate taxes when we are on the verge of a recession.(via)