That makes around 1, 1.5 MB per day. It's very little, but if you use it only when you must, and stick to mobile versions of the websites, maybe it could work.

Also don't forget that unless you have manually loaded the GPS files for your area, they will be downloaded from the server as well, and those files take up quite a lot of space.

Download the GPS files from here:
http://www.maemopeople.org/index.php...ut_a_network_c


and also avoid using any sattelite view on GPS as those are downloaded always afaik.