Housebuilder Persimmon is a top riser after it said sales have remained consistent since it last updated the market on March 2, despite uncertainty over the state of the economy and the coming general election. Peers Redrow and Taylor Wimpey are also posting good gains.It's been only seven weeks since it announced its preliminary results but since then the outlook for the first half of 2010 has improved substantially for engineer IMI. The shares are higher today.Turning to the fallers, shares in WH Smith are lower. Revenues were down at the newsagent in the half year to February 28, but efficiency measures helped it post a rise in pre-tax profits.FTSE 250 - RisersIMI (IMI) 680.00p +5.67%Redrow (RDW) 148.80p +4.71%Bodycote (BOY) 219.80p +4.57%Brewin Dolphin (BRW) 144.80p +4.55%Connaught (CNT) 279.40p +3.67%Keller Group (KLR) 702.00p +3.24%Telecity Group (TCY) 418.00p +3.21%Persimmon (PSN) 479.90p +3.05%Dunelm Group (DNLM) 408.10p +3.03%Taylor Wimpey (TW.) 40.19p +2.89%FTSE 250 - FallersCSR (CSR) 449.20p -3.52%Ferrexpo (FXPO) 352.20p -3.32%JKX Oil & Gas (JKX) 273.60p -3.22%Hochschild Mining (HOC) 267.20p -2.69%COLT Telecom Group S.A. (COLT) 133.20p -2.49%Enterprise Inns (ETI) 132.10p -2.44%Talvivaara Mining Company (TALV) 466.80p -2.40%WH Smith (SMWH) 502.50p -2.33%DS Smith (SMDS) 140.00p -2.10%Drax Group (DRX) 369.00p -2.04%