Does YSlow handle DHTML? Ajax? Web 2.0?
Many web pages are moving to a Web 2.0 style where the components in the page and the page itself are built dynamically in the browser using JavaScript. The main function behind Ajax is XMLHttpRequest. Similar functionality can be achieved using JSON and hidden iframes. YSlow analyzes all the components in the page, including components downloaded using these Web 2.0 techniques. If these dynamically loaded components are missing an Expires header or aren’t gzipped they will be reported by YSlow, as expected. If your Web 2.0 page dynamically downloads components after the onload handler or uses Ajax, you can measure these components by disabling the YSlow Autorun option, and instead launching YSlow manually after all these requests are done.
