Block access to web based chat messengers and IM like gtalk , msn or yahoo in your office or school without blocking the whole site itself using the Hosts file.
For example in iGoogle there is an option to add these messenger modules(gtalk,msn,hotmail & yahoo). And with this trick you can block only these Messengers but not the whole IGOOGLE itself.
First of all,Open the hosts file located in C:windowssystem32driversetc with your notepad.Add these following lines in the hosts file and save it.
More messengers can be blocked by adding the server address of the messengers to this file.With this the Gtalk module in the Gmail page is also blocked.