How can I launch a javascript from an <iframe>?

There is an iframe on the page.

Can the parent document (iframe parent) be accessed from this iframe?

What I want to do: when the user presses a button inside iframe something happens on the main page

Thanks!

you tried parent.?

In my experience, it works, as long as its the same domain.

If I understand correctly, this behavior is not allowed. An iframe would contain contents from some other domain, and if that domain could issue code to affect the elements of the first domain, security ruin would ensue. Read this info about the same-origin policy: http://en.wikipedia.org/wiki/Same_origin_policy