how to show page on the parent of the iframe

Question

index.html is :

<iframe src="/changeDataAndBack"></iframe>

but the html file return back is show in the iframe ,

how to show page on the parent of the iframe

thanks

updated:

i changeed to this,but nothing happend :

<iframe src="/_openid/login?continue=/" target="_top"></iframe>

Answer 1

it is ok now ,i add target="_parent" to iframe page :

<form class="openid" method="post" action="{{login_url}}" target="_parent">