Your site is initially deployed using a self-signed SSL server certificate. Some browsers will display a warning message such as "This connection is untrusted." In this particular case, you can safely tell your browser to trust this certificate. Only people who visit your site over HTTPS will see this warning. The only people who need to do this will be those who log in to your site, such as yourself and other content editors.
IS&T updates sites periodically to replace self-signed certificates with InCommon certificates. InCommon certificates are available free of charge, but since they require some staff time to request and install, we periodically request them for sites which appear to have production-ready names, and which appear to have been configured.
If your site is nearing official deployment, and you would like an InCommon certificate for it, please let us know at email@example.com; please allow turn-around time of two days to a week on this.