I had someone create a bogus yahoo e-mail and make it appear that it was me and sent out very humilating e-mails with this e-mail. I paid to find out the name of the account, but they just used bogus info to set up the account. Is there a way I can get the IP address or trace the original e-mail?

I need to find the IP address (or the MAC address) of the actual machine that is using my web application. Getting it from the server variables at the server end will not work because the user machines are behind proxies. I need a client-side scripting solution. The users are agreeable to the web application checking for their machine IP and will allow it.

I am trying to estimate what percentage of the time the city attributed by an IP address locator is correct. Specifically, I am interested in the performance of a Google PPC campaign.