Testing and Optimizing of what I call "traditional" page-based web applications is not too hard to do. Take CNN as an example. You have the home page www.cnn.com. From there you can click through the news sections such as U.S, World, Politics, ... - each click loading a new page with a unique URL. Testing this site is rather easy. Use Selenium, WebDriver or even a HTTP Based Testing tool to model your test cases. Navigate to all these URLs and - if you are serious about performance and load time - use tools such as YSlow, PageSpeed or dynaTrace AJAX Edition (these tools obviously only work when testing is done through a real browser). These tools analyze page performance based on common Best Practices for every individual tested URL.
Read the rest of the article where I explain what the Best Practices approach misses, how we can best test web 2.0 applications using Selenium/WebDriver and how to analyze and optimize performance of user interactions.