So basically this allows you to be invisible and still see messages while the person who sent you the message still thinks you haven't read it cause the "Message Not Yet Delivered" symbol will still be beside their messag they sent, so to sum up what im saying, you can spy on what they say to you when you become invisible and they think you haven't got their message yet, enjoy!
Step 1: Open any window eg Notepad.exe or anything that has a "X" at the top for you to close
Step 2: Go to Skype and find the person you want to spy on when you go invisible
Step 3: Make your status "Invisible"
Step 4: Go to the person you want to spy on and do what i did in the picture below
Then let it sit like that and you can see everything they text you!
And that's about it guys, pretty cool, I use it a lot and figured I'd share.