I used some tool to check invisible yahoo but almost of that return wrong result so i update my tool. Now, it can detect Yahoo Invisible. You can do that in 15 seconds:
Visit http://tools.vngoogle.com or http://tool.vngoogle.com
Copy link and send for someone you need to check
Waiting 10 seconds
Click on Get IP button
The result will provide for you Which status of yahoo user. If they online, you can get IP and their location.
How to it work.
When you send a link to yahoo. The yahoo messenger Program will auto load the picture. It will visit my server and My program on server will catch the IP. So
If invisible or online => You will receive their IP
if they offline => nothing loading..., NO IP, NO location ...
If they using mobile chat... i'm sorry, i can't check it.
It's available on Yahoo 11 + (all version)
