You can do that with a javascript that loads a new
window.location.href = 'http://newlocation.com';
You can also use trasitions in styles as the previous example.
The new features of the htmlviewer are worth alot since they open a full set of usages to xojo developers. You can even communicate to and from javascript to Xojo now.
Your old usage style is not recommended. Laying controls on eachoter is pretty bugged sometimes.