Ahh ok, I thought it was odd. just didn't realise it hides and then shows, just looked like a refresh.
In that case put the <a name="xxxx"></a> below the tabbed box.
The content seems to always be inside a container that should stay the same size.
Wrap it all inside a containing div with a set height that way, that element will always be present, the page will stay the same size and the scroll bar won't disappear, eliminating the jump to top.
May seem like a minor annoyance for you as you've seen it so often but as a new visitor, someone may find it annoying, give up and leave the site...