I've known a technique to reveal the invisible contact in the YM, but was reluctant to discuss it due to the nature of the technique. Hohoho. Well, suffice to say that it's illegal.

However, that's not the case anymore!

We can do this the right way. All you need to do is know your friend's username on yahoo. This service is provided at Invisible.ir. Just key in the username and the system will reveal if they're online or not.

Cool!