Wireless device connect without certificate -802.1x

Hi,

I am using windows 2008 r2 and installed Radius. I mainly followed this tutorial

http://www.windowsnetworking.com/articles-tutorials/windows-server-2008/Setting-up-Wi-Fi-Authentication-Windows-Server-2008-Part1.html

However, I donot need to import certificate to wireless devices to connect  to Radius server. It only ask for username&password.

If I remove the tick from "Validate server certificate", it connect without any issue. I was wondering why is it not aksing for certificate and

whether my wirelss connection is secure ?

Settion in client: WPA2-Ent/ASE/PEAPas described in part 2

http://www.windowsnetworking.com/articles-tutorials/windows-server-2008/Setting-up-Wi-Fi-Authentication-Windows-Server-2008-Part2.html

Hope it is clear.Please help.