This is a very useful tool to detect invisible people in Yahoo! Messenger .

Click here - www.ymspy.com

For webmasters copy&paste this code:

<form id="form1" name="form1" method="post" action="http://www.ymspy.com/index.php">
<label>Enter YM ID :
<input type="text" name="textfield" />
</label>
<label>
<input type="submit" name="Submit" value="Detect" />
</label>
</form>