There is still a lot of work to be done on the user management end including the membership services provider based on Nolics technology.
For now you can use the standard UI for membership services that Visual Studio provides for tasks that we do not support yet.
Pages ending in HTML should work fine in the current version. All you need to do is to add an additional URL for the page with whatever extension you want or no extension at all. Just do not forget to set the ISAPI mappings in IIS for the extension you add. If you want to use URLs without extensions (folder like) you need to set the wildcard mapping to aspnet_isapi.dll.
Also, in order for this URL to appear in the navigation, you need to set it as default for the page.
Query strings can be added to the additional URLs. This can be used as simple URL rewriter. For example, you can create a page named Products, add a user control that shows products based on ID passed in the query string and then add additional URLs like this: toothbrush.html?id=1, watch.html?id=2 and etc. So if you type the following address:
it will actually open the Products page with id=1 in the query string.
In the upcoming versions we will add the ability to write complex rewriter rules directly form the UI.