Stocks are heavily under pressure today amid growing concerns over the Eurozone crisis. Meanwhile travel group Thomas Cook's share price is taking a severe battering.Thomas Cook's shares are down by more than a quarter now after it said its third quarter results will miss expectations as the turmoil in the Arab world and economic weakness in the UK take its toll on the travel operator. The firm said its French operations have been hit particularly hard by the political unrest in countries such as Egypt, Tunisia and Morocco. Peer TUI Travel is also hurt.Oil outfit Premier Oil moved to assure the market about production targets saying it predicts a sharply increased production rate of around 60,000 barrels of oil equivalent per day by the end of the year, as its Asian development projects ramp up output.Information technology solutions provider Computacenter said profitability in the first half of its financial year will be comfortably ahead of the same period last year, and trading at this stage remains in line with management expectations for the year as a whole.Turning to smaller companies, scheduling and operations management software provider ServicePower Technologies is higher after saying it expects to report results ahead of expectations for the six months to 30 June after a busy period for the company. Investors in Yellow Pages publisher Yell have something to shout about after it announced a tie-up with operating system giant Microsoft to provide advertising for small and medium businesses. Yell said it would be teaming up with Microsoft to offer search, mobile and local advertising services to small and medium businesses to make the most of new business models arising from the growth of "cloud" computing.Among smaller companies, Arcontech, which supplies real-time software to investment banks, is going great guns after announcing new contracts for its software. "The sales have been made to a diverse client base ranging from a smaller independent investment bank to a large international banking group," Arcontech said.FTSE 100 - RisersMarks & Spencer Group (MKS) 374.10p +1.46%Next (NXT) 2,387.00p -0.04%GlaxoSmithKline (GSK) 1,356.00p -0.11%Capita Group (CPI) 699.50p -0.14%British Land Co (BLND) 586.00p -0.26%Land Securities Group (LAND) 839.50p -0.53%Hammerson (HMSO) 454.50p -0.53%Experian (EXPN) 799.00p -0.56%Kingfisher (KGF) 255.90p -0.62%Centrica (CNA) 321.80p -0.68%FTSE 100 - FallersARM Holdings (ARM) 596.50p -4.94%Wolseley (WOS) 1,900.00p -3.75%International Consolidated Airlines Group SA (IAG) 229.10p -3.41%Barclays (BARC) 226.15p -3.33%Lonmin (LMI) 1,347.00p -3.02%Tate & Lyle (TATE) 607.00p -2.80%Xstrata (XTA) 1,329.00p -2.71%Old Mutual (OML) 130.00p -2.62%Rio Tinto (RIO) 4,339.00p -2.49%Vedanta Resources (VED) 1,863.00p -2.46%FTSE 250 - RisersDaejan Holdings (DJAN) 2,799.00p +1.74%Informa (INF) 428.10p +1.49%Dunelm Group (DNLM) 470.70p +1.40%WH Smith (SMWH) 524.50p +1.16%Kesa Electricals (KESA) 137.80p +1.10%Laird (LRD) 192.00p +1.05%De La Rue (DLAR) 736.50p +0.89%BH Macro Ltd. EUR Shares (BHME) € 17.10 +0.88%Bwin.party Digital Entertainment (BPTY) 140.10p +0.79%Hansteen Holdings (HSTN) 84.60p +0.71%FTSE 250 - FallersThomas Cook Group (TCG) 88.80p -27.63%TUI Travel (TT.) 207.30p -6.28%Jupiter Fund Management (JUP) 241.30p -5.74%Yule Catto & Co (YULC) 229.20p -5.68%Premier Oil (PMO) 412.70p -5.08%Centamin Egypt Ltd. (CEY) 121.00p -4.42%Misys (MSY) 396.30p -4.18%CSR (CSR) 304.00p -4.16%Logica (LOG) 121.50p -4.10%Aquarius Platinum Ltd. (AQP) 299.50p -3.91%