iframes and anchors

Hi All,
I've had a good google for the solution to this problem but I can't find
one.

I have an iframe within a parent window. When I use anchors to position the
iframe window, the browser scrolls the parent window such as to place the
contents of the iframe at the top of the browser. This is incorrect
behaviour. How can I get the browser to leave the parent window alone but
just scroll the child iframe to the requested position?.

Thanks in advance,
Dave