I think you need to provide a little more info but for starters:
What are u using to access the admin page?
http://localhost:8080/admin?
if so, check that "localhost" is mapped in your hosts file.
Check that your server is up.
Check that you app is running on port 8080, or whatever port your
using.
If you are in a network that uses a proxy to access the internet, make
sure "localhost" is listed in the Exceptions list for the proxy to
bypass. (ie. Tools, Intenet Options, Connections, Lan settings. Of Use
proxy server is checked, click advanced and add localhost to the
exceptions list)
If those are not it, what kind of page is showing up?