If you have not yet launched a docked application, its icon tends to have three dots on it. When sufficiently clicked upon, the app will load and the dots will disappear. If you want another instance of the application (it may be an xterm or something), you have to right click on the icon and hit launch. However, doing this also creates another appicon for it, cluttering up your desktop. To alleviate this problem, load one instance of the application, right click on the titlebar and select
attributes. From there, go to
Application Specific and check the box beside
No application icon. Hit save, quit the app then try launching a few. You'll find that the dots now persist and you don't end up with extra icons. Not only that, but you can launch several copies of the app (handy for xterms) without extra effort.