JS guru needed for a small task

We have an iframe provided by our adserver, this iframe serves targeted ads based on content. We want to get content from parent page in order to serve ads in the iframe so added this into the iframe document = [login to view URL] . The issue is the iframe domain and the parent domain are different so we are getting unauthorized alert. We need to find a work around for this. We have to mention that we have no control over the parent page so the fix must be applied from within the iframed page.