Invisible-check ICQ numbers

Probably everyone faced with the fact that it was necessary to find out in the network of people or not. This is especially true when you notice that your customer appears less and less often on the network and is silent ...
I found an interesting site that allows you to check for the presence of the user in the network, even if he has set the status “Invisible”.
Here is a link to the site . Also there you can find a special plugin for Miranda IM , which will allow you to find any user hiding from you.
The site offers different ways to check:

1. Anonymous for icq5, Miranda IM and Trillian
2. Non-anonymous for all customers
3. Difficult, but anonymous for all customers.

I tested it on several numbers, which are not even in the contact list - everything, surprisingly, works.