Sounds to me like your Parallels config is set to Host-Only networking for the Guest.
Switching to Shared Networking should give your guest Windows OS a local IP address.
Then, you will have to access the Windows local IP address (not 127.0.0.1) from the Mac browser. You can find out the IP address to use by opening a command prompt in the Windows guest and taking a look at the output of the ipconfig
command.