czernowitz,
Whenever posting questions on these forums, please give us as much information as possible about your computer. Depending on your issue, we might need the operating system, processor speed, amount of RAM installed, and any other information you think might help us. (In this case, we certainly need the type of internet connection you have installed...Dial-up? Cable? DSL? something else? The more information you give us, the better informed our answer will be.
In the meantime, if you're using a dial up connection, there normally is a setting in the ISP's dial up connection properties, or the "dial-up networking" section, which will allow the connection to immediately shut down after closing the browser. Since you didn't give us your operating system, or such, I can't give you specific instructions on how to gain access to that section, but it should be there.
Hope this helps and let us know....
Grif
What is the procedure, when
exiting from Netscape,
it will also disconnect
from internet.

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