You can upload the sgf file as an attachment, preview it, and then copy the URL for the link in the preview into your post to put it between the sgf tags. That way the file will be saved on the server here and be referenced correctly in your post, and you don't need to get the URL to the KGS archive or any other site.

Hello,
I read all the topic, But in my topic, i have this problem: "Received invalid game data".
My topic: viewtopic.php?f=4&t=11436

I'm sure that the .sgf file is right and the link on sgf tag that i put, is working.
I have already tested the link on forum and the file inside him. The sfg file was created by my on Eidogo.

I don't know why it's cannot showing the sgf file correctly on topic =/
Does anyone can help-me?

Thank you for attention!

Would have worked. You need to preview your post and then copy the link from the attachement link that appears below the preview, not use the link that you get after you upload a file. If that makes sense.