JSF 1.2 is the latest release of the JSF 1.x specification and it works with Servlet 2.5 and JSP 2.1.
JavaServer Faces (JSF) is a user interface (UI) framework for Java web applications.
JSF 1.2 is a specification driven by the JSR-252 expert group under the Java Community Process (JCP).JSF became part of Java EE with this 1.2 release.
Unified Expression Language (EL) a major change in this specification , deprecates the Faces EL of its predecessors.
At a fundamental level, JSF is a way to get values from the user, into the model tier for processing.
See jsf for more information.
Migrating from JSF 1.2 to JSF 2.0: here