Liberada, it's called a "widget". You can click on the button below anyone else's you see or here's the site:

http://www.widgetbox.com/

I think you want a gadget/counter. If you see someone's you like here on this site you can click on their button and it will take you to the page of the one they chose at widgetbox. For example, here's Brian's:

http://www.widgetbox.com/widget/countuptimer

You personalize it and "Get Code" and then put the code in your signature box here in your Personal Profile.

They're not part of this site and some people don't like them in others' posts (like I might not like it in yours) because it can make pages load slower for them and there's nothing they can do about it.