Hello Aruna,
First thing you need to check is whether the problem is machine specific. Check with user if he is able to access from another workstation (where it works for any other user)
If its working from another workstation, then its clearly machine specific issue.
In that case verify the IE proxy and other settings.
If its not working from anywhere, then check if this particular web app is configured for NLB and is the user able to ping the web app from workstation
::> Ping www.yourWebApp.com etc.
In that case, also apply the solution provided by Sushant.
Hope this helps,
Regards, Rohan --Please mark as "Answer" if the post resolve your issue--