I noticed that in Firefox I can add a #MyAnchor tag to the action attribute like...
You can deal with this either on the client side or on the server side:
On the server side: add a hidden element with the anchor as the value and do a redirect on an URL build on the server.
On the client side: jQuery for instance allows you to serialize a form's parameters into a URL; you would just need to append the anchor and assign this to window.location.