Can't navigate and access the web after reset

I just bought an HTC Tattoo. I tried it, I connected to my home wifi network and visited a couple of sites. Then, since I saw that the guy who sold it to me had already put some information on it, I had the bad idea to reset it. Now it detects the wifi network and correctly connects to it (after inserting the correct pass, it's protected with WPA2). However, when I open the browser, or google maps, or try to setup a google account, it cannot reach any page. A guy on another forum suggested me to set the we options for my carrier. I didn't do that since I didn't want to connect using UMTS or GPRS, What do you think I have to do?