First try to access the weblogic page. http://yourwebserver/index.html
just to make sure that at least your weblogic is properly configured.
If you get a web server index page, then your error is probably a mistyped URL, or a problem with a configuration.properties setting. Could be a port error, maybe the app server is not listening on the same port.
If you have IIS enabled there could also be a port conflict. I use port 8080 with weblogic.
If you change the port setting, you must specifiy it in the URL, e.g. http://yourwebserver:8080/psp/sitename/?cmd=login
Also, try using the IP address instead of the DNS name for the web page, it could probably be a name resolution problem.
Let's start with the above and please inform on your results.