Hey fellas. I saw that site on a search last night.
When you do not have proper SSL certificates in place or updated, you will get that warning page from your browser. By accepting or continue you are safe to visit the site. I would not put any personal information that you do not want the world to know in a form on a site like that, but posting and browsing are safe.
My web application ran like that for 2 years just fine because we did not want to pay for the services for security and we only have a few people using it. Any site with 20+ regular users should get that updated though.