Hello delliot,
SSL VPN and Web VPN are the same terminologies. Since the VPN is accessed over HTTP or Web, they used to call it a WEB VPN. They also re-named it to SSL VPN since it uses SSL as the transport layer technology. So, you dont need to get confused on this...
I guess all versions of ASA supports SSL VPN. But by default you will just have 2 licenses of SSL VPN inbuilt on the box. If you need more licenses, you can procure the following product codes:
ASA5500-SSL-10
ASA5500-SSL-25
.
.
ASA5500-SSL-5000
Just give a "show version" and see if you have the SSL VPN licenses inbuilt on the ASA box. You can see 2 licenses included with the box. you can also try configuring some SSL VPN commands to see if the box supports it or not !!!!
Hope this helps.. all the best.. rate replies if found useful..
Raj