i would say php, and possibly mysql, these are probably the most widely used and supported on teh internet, also are relatively easy to learn, that site ou mentioned is also made from php, so it shows it is possible and www.hotscripts.com ahs a lot of scripts that could get you started, and maybe you could modify them, imo the best way to learn a language is to look at an example, then break it down and learn each stage
do you mean what language they use?
I think ebay uses some form of java, as if you notice on the homepage it says powered by sun(who make java) unless that is just the servers
and i would say google use their own language, or one that isn't [easily] accesible by the public
Ebay was made using C or C++. I'm not sure what it stores its data with though.
The best order to learn Web Development in would be as follows:
1. XHTML and CSS
2. Java Script (Some thing usefull. Not anoying little scripts you get hasteld by at some sites)
3. PHP and MySQL