Have a look at the following investigation by Sam Allen..... "The author developed a program to snapshot memory usage per process every 3 seconds on Windows. Using this he recorded 3 hours of memory usage for five different browsers under real-world usage scenarios: Safari 3.1, Firefox 3, Flock 1.2 (a browser based on Firefox 2), Opera 9.5, and Internet Explorer 8. A million data points indicate that Firefox 3 has a surprising advantage over the other browsers tested. These are real-world tests and ......