Coach Wei, of Nexaweb and Apache, has published a study of Ajax performance issues in browsers, and they won’t surprise you:

Obviously, we would like to see browser vendors take a serious look into the following issues and put them on their roadmap:

1. In all major browsers, performance with Array and HTML DOM needs improvement in general.
2. Browsers need to provide API support for Computed Box Model and Style;
3. FireFox needs to improve performance of “eval”, object creation and “in” operation
4. Internet Explorer needs to improve performance in general to be at least on par with other browsers. Beyond that, “String” manipulation on IE needs continued improvements;
5. Safari: “pop” operation performance needs improvement
6. Just-in-time (JIT) compiler: This maybe a bigger task than an incremental fix of some existing features, however, it is worthy of every penny. JIT will not only fix the String manipulation issue, it will enable JavaScript to truly shine in matching the performance of native applications. The amount of client side logic (aka, JavaScript code) needs to grow in order to accommodate the growth of application complexity, for which JavaScript runtime performance problem can be a major bottleneck.

Read the study to get the details on each item. It includes the results such as the DOM operation performance information: