How to check whether person is Invisible or Online without Yahoo Messenger

How to check status of yahoo messenger at schools, colleges or office where yahoo messenger is not available.
How do I find out if a contact blocked me in the yahoo Messenger?
How can you check if someone has blocked you on yahoo messenger?

step1:
copy paste this url on your browser
http://opi.yahoo.com/online?u=yahooid&m=g&t=2
step2:
replace text yahooid with your id

ie suppose your yahoo id is "adkool" then statement
http://opi.yahoo.com/online?u=yahooid&m=g&t=2
will become
http://opi.yahoo.com/online?u=adkool&m=g&t=2

If a user is online and appears invisible to you, you get the status as Online.

How do I find out if a contact blocked me in the aim Messenger?
How can you check if someone has blocked you on aim messenger?
Aim Status Checker is a web based tool. You can use it to see your friend is Online or Offline on Aim Messenger.
http://www.aimblockchecker.net/

How do I find out if a contact blocked me in the msn Messenger?
How can you check if someone has blocked you on msn messenger?
Msn Status Checker is a web based tool. You can use it to see your friend is Online or Offline on Msn Messenger. You can use it to detect if someone has blocked you. If your Msn Messenger is not signing in, you can use this tool to check whether your friend is Online or not.
http://www.msnblockchecker.info/