Security vulnerabilities found in Microsoft’s Internet Explorer may be having an effect on the Web browser’s market share, according to WebSideStory. Over the last month, usage of Internet Explorer dropped by 1% (from 95.73% to 94.73%), the first noticeable decline since the Web metrics company began tracking the browser market in 1999. Mozilla and Netscape’s combined market share has increased by 26%, rising from 3.21% in June to 4.05% in July.