Europe\'s main stock markets slid at the start of trading on Friday, with bank shares the biggest fallers after Moody\'s credit ratings agency downgraded some of the world\'s biggest lenders. London\'s benchmark FTSE 100 index dropped 0.84 percent to 5,519.58 points, Frankfurt\'s DAX 30 slumped 1.1 percent to 6,273.10 points and in Paris the CAC 40 lost 0.76 percent to 3,090.41. The health of 15 of the world\'s largest financial institutions has been called into serious question after Moody\'s downgraded their credit ratings, citing risk exposure and the eurozone crisis. Some of the biggest names in banking -- including Goldman Sachs, Barclays, Citigroup, HSBC and Deutsche Bank -- saw their ratings slashed on Thursday after the close of US markets, spelling increased investor scrutiny and potentially higher borrowing costs for lenders. At the open on Friday, HSBC shares fell 0.6 percent and Barclays slid 2.0 percent in London. In Paris, shares in BNP Paribas dropped 1.25 percent, Credit Agricole by 1.5 percent and Societe Generale by 1.18 percent. Europe\'s main stock markets were also lower after losses for equity indices in Asia and on Wall Street overnight in the wake of weak manufacturing data from China and Europe, traders said. The US Federal Reserve\'s light-touch stimulus on Wednesday also weighed on share prices with concerns it would not be enough to boost the stuttering economy.