I am fairly new to encryption and SSL. Today I googled a bit (read some atricles about security) and encountered the site https://cacert.org. I clicked it and was surprised. Chrome showed me a "not trusted" error. The SSL certificate seems not to be valid. I looked up the certificate and it shows me that the certification agency is not trusted anymore. I got some questions now:

• Isn't CAcert a certification agency itself?
• Why is that?
• Could this be some kind of attack approach? (MITM)
• What can I do?
• Where can I get more information?