The IE team has published a new whitepaper describing IE 6 security. Get it here:
Understanding Security in Microsoft Internet Explorer 6 in Windows XP SP2
Web browser security is a major concern for individuals and organizations. Each time a new vulnerability is found, news headlines proclaim dire warnings. As a result of their importance, security issues dominate competitive browser analysis and discussions, overshadow debate about their respective features and functionality. As the market share leader in Web browser software, Internet Explorer (IE) is often the subject of media scrutiny. Since IE is so prevalent, it is an attractive target for hackers to attack, and has come to be considered, in some circles, insecure. This paper examines the real state of Web browser security and the correlation between a browsers vulnerability and its advanced functionality.
This paper isn't targeted at developers, but it gives a good overview of the security features in the browser.