ICQ has a feature to show your online status on a web page. You need to enable it in the "Security and Privacy" settings as indicated on ICQ's support page.
Once you include http://status.icq.com/online.gif?icq=<ICQ-ID>&img=5 in a web page you can show your online status like this: 
(Online) and 
(Offline).
Now the page that used to show all the icons available (img=<number> parameter in the URL) 404's (with a very nice 404-cow). Try at http://www.icq.com/features/web/indicator.html whether ICQ fixed their pages.
A friendly
helped to get the Online (and similarly the Offline) icons in the mean time.
Looking at them I find these icons provide a nice glimpse into web design history.
ICQ was founded 1996 and has seen a lot of changes between being sold to AOL 1998 and on to mail.ru in 2010. Aah, the '90s ... animated gifs anyone?
As you probably risk eye-cancer looking at them too long, the full glory of the available ICQ icons delegated to the full article view...
Thanks for the detailed info
) I haven't used icq in ages and client poped up with a request to add this to the website 
cause he works with Russia alot and they do use icq 
So this was really helpful
http://www.icq.com/features/web/indicator.html does not exist
I said so in the blog entry and it still has not been fixed at ICQ.
Archive.org's wayback machine has working versions of the web page from 2011 and earlier:
http://web.archive.org/web/*/http://www.icq.com/features/web/indicator.html