Standard & Poor's has lowered credit ratings on Dow component Bank of America (NYSE:

) and Citigroup (NYSE:

) to A- from A. The A level is still investment grade and implies "strong capacity to meet financial commitments, but somewhat susceptible to adverse economic conditions and changes in circumstances," according to the S&P Web site. A plus or minus sign is used to show relative standing within the major rating categories. BofA plunged more than 3% today while Citi closed modestly higher.