How to use GPRS (not wifi or 3G) to get internet access? With my Galaxy 5, I can visit websites using wifi, but how can I access them using GPRS (=when no wifi around)? I don't want to pay for a 3G data plan with my mobile operator.

Background: On my old Nokia phone (which didn't have wifi), I was able to visit a website using GPRS (useful only for emergencies, but still, useful). This meant that I did not have to subscribe to some data plan with my mobile operator (at least in my country this is so); I did have to pay for the GPRS connection, but that was only when connected.
This sounds like something that you need to make sure your operator has enabled on your contract, normally with smartphones a data plan is a data plan, once you've got one they give you a (monthly/weekly/daily) bandwidth limit which you can use either on 3G or GPRS, the operator doesn't care which you use.

It sounds like you don't want to pay for a monthly data limit, you want to get a metered contract where you only pay for when you use it (normally charged by the megabyte or by the hour, or something similar).

You can then turn the data connection on or off depending when you want to use it. The exact setting for this can vary from phone to phone, but is normally under something like Settings -> Wireless and Network -> Mobile networks -> Use packet data. On many phones you can also switch to only use GPRS or 3G (sometimes called GSM and WCDMA modes) but all that does is control the speed of your connection, not normally how you're charged.