I have installed tomcat 5.5.12 and have successfully deployed a J2EE project. But the next day when i tried to access the project folder I got a HTTP 404 error stating that the resource is not available.
what's wrong? One day I am able to access the project, and the next it says resource unavailable
Are the services still running? if its the next day you may have restarted the OS. The Tomcat services may no longer be running -> could be set to Automatic rather than alway in XP's services folder, the /etc/init.d folder will likely contain the process control in unix/linux so you can check its status there.
Also, your IIS (XP) or your httpd in unix may not be running, thus you would effectively not be running a web host.
Check the logs. There could be something wrong with the settings in your web.xml.