A fluid lay-out is page that is user-agent agnostic and simply reorganizes the page based on the dimensions of the browser window. You can preview the mobile page by simply shrinking the browser window.
Is it me or is the combo of a fluid layout + ajax calls ruining web browsing? It takes 8 seconds to use CNN.com because the pop-in from AJAX calls results in a constant reorganization of the site. Yahoo.com requires that I refresh it TWICE in order to see the latest news, an issue that is made worse by Chrome on Android forcing you to stop the page before you can refresh it (menu button, stop, menu button, refresh, menu button, stop, menu button, refresh). theonion.com was horrendous when it first switched to the fluid layout; its still bad but at least the auto-playing video ads (with sound) at the bottom of the page are gone, and the back button seems to work properly now. There's nothing wrong with the idea of a fluid lay-out, but the execution of it always seems to be terrible.