What do I need to know to design something like Craigslist?

Question

i know html. i guess i also need to know cgi. anything else? thank you

Answer 1

Sounds like you probably need some web programming and also a database.

I would try PHP and MySQL.

Another option is Ruby on Rails.

Answer 2

I would say go for php or asp over cgi(perl).  The one you choose will depend on the kind of server you will run it on.  If you plan on running it on a linux server (which is what most hosts are) then use php.  If it's a windows server running IIS then go for asp.

php is probably the best bet.