I believe it is related to the SSL certificate having expired. This allows the site to run on a secure https:// instead of http://
Its a technical problem that would require the webmaster or provider to fix. I think the main point is, data you send to the server as users is potentially not encrypted. So long as you aren't entering any credit card information or using the same passwords you use on important sites, I don't think it would be a major problem until fixed.