Mining stocks were the best performers today, following the decent economic data from top metals user China. African Barrick Gold, BlackRock World Mining and Polymetal were three of the strongest risers on the second tier this afternoon. UK regeneration specialist St. Modwen Properties jumped as it beat forecasts with a 32% increase in half-year pre-tax profit. The company also said that improving valuations, particularly in the residential sector, underpin its confidence for the full year. Online retailer AO World recovered from yesterday's falls, when it was hit by an initial 'sell' rating from Shore Capital.Meanwhile, Ocado was the day's biggest faller, hit by concerns about growth, despite it saying it was set to deliver its first ever pre-tax profit. The company did note a slowdown in sales and said that growth was limited by "subdued and cautious consumer spending". Shore Capital said it sees "vulnerabilities" in the online grocer's business model, reiterating its 'sell' rating. NMC Health retreated from its recent surge, which was yesterday driven by the news its Chief Executive Officer and founder, B R Shetty, had purchased 10m shares from its largest shareholder at a price of 500p per share.Synthomer shares were hit by the news Adrian Whitfield, its Group Chief Executive, is planning to step down after eight years with the company in June next year. The specialty chemical company said it would conduct a comprehensive search for his replacement.FTSE 250 - RisersAfrican Barrick Gold (ABG) 220.30p +7.10%St. Modwen Properties (SMP) 375.70p +4.77%Entertainment One Limited (ETO) 323.60p +4.39%BlackRock World Mining Trust (BRWM) 481.80p +4.04%Keller Group (KLR) 956.50p +3.85%AO World (AO.) 267.20p +3.77%Paragon Group Of Companies (PAG) 364.50p +3.52%UDG Healthcare Public Limited Company (UDG) 353.70p +3.27%Poundland Group (PLND) 326.60p +3.03%Polymetal International (POLY) 595.50p +2.94%FTSE 250 - FallersOcado Group (OCDO) 354.40p -4.55%Genus (GNS) 1,099.00p -4.18%Investec (INVP) 523.50p -2.88%NMC Health (NMC) 485.80p -2.84%Exova Group (EXO) 239.50p -2.64%AL Noor Hospitals Group (ANH) 1,000.00p -2.15%Fidessa Group (FDSA) 2,172.00p -1.90%Riverstone Energy Limited (RSE) 910.50p -1.57%CSR (CSR) 583.00p -1.52%Synthomer (SYNT) 228.60p -1.51%NR