Advertising and marketing group WPP, led by chief executive Sir Martin Sorrell, said the "post-Lehman bounce-back" has continued as it posted pre-tax profit growth of 37% on sales that grew 6.1% in the six months to 30 June."Despite recent uncertainties, these results continue the post-Lehman bounce-back seen in 2010 and the group has now achieved levels of pro-forma revenues and profitability beyond 2008," the firm said.Reportable revenues grew 6.1% from £4.44bn to £4.71bn, helped by strong growth in the emerging markets. This was an 8.1% growth on a constant currency basis, reflecting the strength of the pound sterling against the US dollar. Billings rose 5.2% from £20.33bn to £21.39bn.Meanwhile, pre-tax profit surged from £243.9m to £334.3m. Basic earnings per share rose from 12.3p to 18.5p, a 50.4% increase.The decent results helped the firm to raise its interim dividend per share by 25% from 5.96p to 7.46p.Despite Nomura expecting the firm to give up on its 6% revenue growth target for the full-year, WPP has remained optimistic, saying that any slowdown experienced in the US should "be balanced geographically by faster growth in the UK, Western Continental Europe, from admittedly low levels, and faster growth in Asia Pacific, Latin America, Africa and the Middle East and Central and Eastern Europe.""So in summary, so far so good in 2011, with forecasts in reasonable heart, but there are storm clouds and we still have to see how the latest stock market crisis affects consumer and client thinking and actions," WPP said.BC