Hello, rumisha.
Here is an article that will help you troubleshoot the connection to the iTunes store you are experiencing on your iPod Touch. Scroll to the section labeled Troubleshooting on an iPhone, iPad, or iPod touch. Attempt to connect to another wifi network to see if the issue persists as this could be the cause.
Can't connect to the iTunes Store
http://support.apple.com/kb/TS1368
Also, check the date and time. I have attached a screen shot as this could cause an issue if not set correctly.

Cheers,
Jason H.