HTTP 404 errors in websphere:

HTTP 404 errors can have different underlying causes. Some examples of these causes are:
Ø External factors, such as a problem in the Web server
Ø Configuration problems, such as an incorrect Web server plug-in or virtual host configuration
Ø Runtime problems, such as an application or application server not started
Ø User or application problems, such as an incorrectly specified URL

The first thing to check is the integrity of the following system components:

1) Web server à Resolve Web server problems
2) Application server àVerify that App srvr is started
3) Application à Verify that App is started

If these are all working properly or you are not sure which application and server are involved, collecting more information like: Error messages, Logs and try to analyze them.
Ø Errors displayed by the user browser, including the URL that failed
Ø SystemOut log data for the app server
Ø If application is deployed to a cluster, you might need to collect the logs from each active server in the cluster
Ø Web server access and error logs