Google issue

I got this message. Can anyone got this and help me out.

Dear site owner or webmaster of gfxshack dot com,
We've detected that some of your site's pages may be using techniques that are outside Google's Webmaster Guidelines.
Specifically, look for possibly artificial or unnatural links on your site pointing to other sites that could be intended to manipulate PageRank. For example, links added as part of a link exchange scheme may be considered excessive.
We encourage you to make changes to your site so that it meets our quality guidelines. Once you've made these changes, please submit your site for reconsideration in Google's search results.
If you have any questions about how to resolve this issue, please see our Webmaster Help Forum for support.
Sincerely,
Google Search Quality Team


Please check my site and tell me what should I do.

They already told you what you should do...

I know but I have 1 million backlinks. I do not know which to remove and which to keep.