set java class path

click on start--->run--->cmd---->ok
cd C:\Apache Software Foundation\Tomcat 5.0\webapps\kk\WEB-INF\classes
where kk is your application folder name copy link and then
set classpath=%classpath%;C:\Apache Software Foundation\Tomcat 5.0\common\lib\servlet-api.jar;
press enter
path is set for servlet