Hi Praveen,

As Matt has suggested, on the surface it looks like npm is being blocked from Internet access.  

If you have to provide a user ID and password to get to the Internet, you will have to supply npm (and possibly git and bower depending on your set up) with your credentials as well. See http://wil.boayue.com/blog/2013/06/14/using-npm-behind-a-proxy/ for a good write up of how to do this from the command line. Some people have better luck using an environment var to provide the credentials.

If that's not the issue, try running the npm command with more verbose output to see if you can get a better handle where the error is occurring. These flags (info | verbose | silly) will give you increasing levels of detail. Start with info and only move on to verbose or silly if info doesn't catch the issue.

$ npm install -g package --loglevel info

$ npm install -g package --verbose

$ npm install -g package --loglevel silly

Cheers!

Greg