Hiding and being invisible
Yes it's possible. Some proxy servers/clients are easy to work around and get the real ip with for example php. To be completly invisible is impossible but to make it really hard to find you is possible.
I recommend you to use tor and privoxy (comes with tor) witch I have not been able to work around yet. So that's good but it often slows the speed alot.
I dont know exactly how but I've heard that u also can get the mac-adress from php to so changing that might do the trick to.
Well ok, this is what i do when i have to be invisible :
1)Reboot my laptop whit a live cd (my favorite is backtrack2); 2)Change the mac-address; 3)If its possible hack a wireless; 4)Use tor whit privoxy (google for vidalia or torks); 5)Do not post personal data; 6)Hack, now you are very very very very very hard to track.
Hope this help.