you could see at this table :
Product Product Version Servlet spec JSP spec
Tomcat 3.1 2.2 1.1
Tomcat 3.0 2.2 1.1
Sun J2EE Reference Implementation beta 2.2 ?
Sun JSWDK 1.0.1 2.1 1.0.1
Sun JSDK 2.1 2.1 none
Sun JSDK 2.0 2.0 none
Allaire JRun 3.0 2.2 1.1
Sun Java Web Server 2.0 2.1 -
Sun Java Web Server 1.1 2.0 -
Sun/Netscape iPlanet Web Server 4.1 2.2 ?
and then findout what version  you use.

Look at the specification of your container.

For example, if you are using Tomcat the following table shows which
version of the Servlet/JSP spec is implemented by which version  of Tomcat.

Servlet/JSP Spec Apache Tomcat version
2.4/2.0 5.5.15
2.3/1.2 4.1.31
2.2/1.1 3.3.2

and you could find high version  of tomcat:
http://tomcat.apache.org
and if you wanna findout what version of jsp  is coded in your project you can see it in the manifest of it's jar files.