When I tried to go online my Compaq Presario SR110nx gave error 680

This error is generally coming from your computer's modem. How do you access the internet? Dial-up, cable, DSL, satellite? If you are using dial up or your phone line is involved, check the dial tone or phone line to correct this issue as well.

Error 680--- No dial tone
A) Test modem by dialling a number through HyperTerminal or phone dialler. This will test the Modem without using Dialup Networking.
B) Make sure you are using the correct and/or original cable. Some modems used specific wiring which is not compatible with standard modem cables.
C) Check that you phone line is working with a normal phone.
D) Make sure the phone line you are trying to dial on is not a non-standard line, this can cause problems also.
E) If all the above are OK then get a new modem or test in a different location.