There are lots of rubbish ip tracing pages out there. I use the TraceRoute on
http://www.all-nettools.com/toolbox which seems pretty good.
An ip trace can give you an accurate location for someone if they have a static ip (an unchanging ip address given to you by your isp). Many people have dynamic ip addresses (which change within a range and are assigned automatically by your isp every time you log on) so they have broadly similar but not identical ips. You then have the complication of people who log on from more than one place and those who deliberately hide their ips by logging in via a proxy server which makes them appear to be posting from an ip that isn't in fact theirs.
This is why ip checking suspicious characters is more of an art than anything else.