The FTSE 100 opened firmly lower on Tuesday morning as investors paused for breath following a decent performance over the last week.London's benchmark index jumped 1.5% yesterday as it continued to rebound strongly after hitting a five-month low of 6,029 last Monday on the back of concerns over a withdrawal of US stimulus and a Chinese slowdown. Nevertheless, in the five trading sessions since, the index has risen over 4.0%."European markets opened tentatively today as investors decided to cash in on yesterday's gains within the equity markets," said Financial Trader Shavaz Dhalla from Spreadex.Sentiment had been lifted on Monday by better-than-expected readings of manufacturing activity from the UK, Europe and the States, which offset continued weakness in economic figures in China."The data was particularly helpful as investors were concerned that a slowdown in China would cripple the overall pace of the global economy. So it seems at least for now, investors are taking a break from panic selling," Dhalla said.FTSE 100: Burberry jumps after upgradeBritish luxury brand Burberry was a high riser this morning after HSBC lifted its rating for the group from 'neutral' to 'overweight' and hiked its target price from 1,530p to 1,750p.Mining stocks were also doing well early on as they tracked metals price higher. Fresnillo, Randgold, Glencore Xstrata, BHP Billiton and Rio Tinto were among the strongest performers.Copper group Antofagasta also gained on the news that it is looking to invest in two hydroelectric power stations in Chile that will provide energy for its nearby project, Los Pelambres. UK housebuilder Persimmon however fell despite saying that revenues rose in the first half as it completed 7.0% more homes than the previous year at a higher average selling price. Jefferies said this morning's statement was "robust" but the stock's valuation appears "full" compared to other peers in the sector.FTSE 250: St Modwen, N Brown impress early onRegeneration specialist St Modwen Properties surged after upping its interim dividend by 10% following an 11% increase in pre-tax profit in the first half. The company hailed an "excellent start" to the year and said it is looks forward to a "successful outcome" for 2013 as a whole.Underlying revenue growth at home-shopping business N Brown accelerated strongly in the first quarter of its financial year with all of its core products contributing, causing shares to jump early on. The company said that like-for-like growth had sped up from 6.1% in the first seven weeks to 7.8% during the first 17 weeks of the year.Online grocery firm Ocado was heading the other way after reporting that it swung to a pre-tax loss of £3.8m in the first half, compared with a profit of £0.2m the year before, as it pumped cash into its growing infrastructure. Underlying earnings however surged by nearly 29%.FTSE 100 - RisersSerco Group (SRP) 656.00p +4.96%Burberry Group (BRBY) 1,414.00p +3.59%Randgold Resources Ltd. (RRS) 4,243.00p +1.43%Antofagasta (ANTO) 843.00p +1.26%Glencore Xstrata (GLEN) 282.90p +1.14%Pearson (PSON) 1,174.00p +1.03%Fresnillo (FRES) 917.50p +0.88%BHP Billiton (BLT) 1,727.00p +0.73%Experian (EXPN) 1,158.00p +0.70%Smiths Group (SMIN) 1,351.00p +0.60%FTSE 100 - FallersARM Holdings (ARM) 784.50p -2.61%Aberdeen Asset Management (ADN) 381.50p -2.58%easyJet (EZJ) 1,318.00p -2.15%Old Mutual (OML) 182.10p -1.89%Tullow Oil (TLW) 1,031.00p -1.72%TUI Travel (TT.) 359.20p -1.56%William Hill (WMH) 449.80p -1.55%Standard Life (SL.) 352.80p -1.48%Travis Perkins (TPK) 1,509.00p -1.44%Rolls-Royce Holdings (RR.) 1,149.00p -1.29%FTSE 250 - RisersSt. Modwen Properties (SMP) 295.00p +7.27%Polymetal International (POLY) 507.00p +4.49%African Barrick Gold (ABG) 103.90p +3.90%Brown (N.) Group (BWNG) 483.00p +3.65%Hochschild Mining (HOC) 160.20p +2.69%Berendsen (BRSN) 785.00p +2.61%Evraz (EVR) 104.60p +2.55%Daejan Holdings (DJAN) 3,655.00p +2.24%PZ Cussons (PZC) 362.80p +2.20%COLT Group SA (COLT) 101.20p +1.96%FTSE 250 - FallersOcado Group (OCDO) 296.30p -5.09%Inmarsat (ISAT) 668.00p -3.88%Inchcape (INCH) 501.50p -2.53%Investec (INVP) 421.70p -2.23%Menzies(John) (MNZS) 690.50p -2.06%Salamander Energy (SMDR) 144.40p -2.04%Home Retail Group (HOME) 137.50p -2.00%BH Macro Ltd. EUR Shares (BHME) € 20.81 -1.84%Imagination Technologies Group (IMG) 288.60p -1.77%Barratt Developments (BDEV) 321.50p -1.71%