Hi Rahul,
Actually that is not our software issue, the IIS in your system is down because of some reason. Just do the following things to solve this issue.
1. Open IIS Manager. (Control Panel ->Administrative Tools -> Internet Information Services (IIS) 6.0 Manager)
2. Double click on the the root of the tree ‘Connections’ (This will be computer name)
3. Click application pool
4. Right click on the default application pool and click start
5. Restart the IIS and try again
:)