Rightmove achieved a 15 per cent increase in underlying operating profit of 49m pounds in the first half as the UK property website secured more advertisers.Profit after tax rose 16% to £34.1m and revenue grew at the same rate to £67.2m in the six months to end of June, boosted by a 3.5% jump in the number of advertisers to 18,916.Average revenue per advertiser (ARPA) was up 14% on the same period a year ago, boosted by sales of additional advertising products and price rises. Underlying earnings per share climbed 19% to 38.4p, reflecting growth in profits and the benefit of shares bought back in the second half of 2012. On a diluted basis, earnings per share were up 20% year-on-year.Traffic was up over 20% on the same period a year ago, driven by an increase in mobile traffic across the company's apps for table and smart phone devices and its mobile optimised website. The latest version Rightmove's app, released at the start of the year, has been downloaded over 3.0m times.Nick McKittrick, Chief Executive Officer, said: "We continue to develop our services to provide the most engaging experience for home movers and the best advertising platforms for our customers to reach the UK's largest home moving audience and to win more business."The company raised its interim dividend by 22% to 11p per share.Shares were up 3.55% to 2,392p at 09:30 on Wednesday. RD