Hi,
First, I would go ahead and load all the uirs and panels at the beginning of the application by calling LoadPanel several times, and having a handle for each panel.
handle1 = LoadPanel (0, "yit.uir", PNLINTRO);
handle2 = LoadPanel (0, "yit2.uir", PNLFOO);
handle3 = LoadPanel (0, "yit3.uir", PNLBAR);
handle4 = LoadPanel (0, "yit4.uir", PNLWORLD);
Then, to display each, you can call DisplayPanel within the button callbacks. In addition to this, you may also have to update the remote panels and register the panel inputs each time. So essentially, each button that leads to a new panel will have some initialization code similar to the code you have written already, and it should update the webpage as you progress and press buttons. Hope this helps!
Jeremy L.
National Instruments