If I would have designed Techrepublic, I would use database tables having fields like user-id, password, question, question-closed(y/n), point etc(and various other tables and fields).
A web application can be written in perl, asp, jsp, servlet, php or coldfusion which will store the user inputs into these tables and also retrieve results on the browser. I would use cookies to store user-id etc on client in case user has,nt logged out(to allow next time logging in without user-id and password prompt).
Techrepublic has probably built a custom application like I have described or has outsourced the work from somebody. Techrepublic best knows the details, I am just guessing.
regards
-mukul