A taskbar button is placed on the taskbar whenever an application creates a unowned primary window. To ensure that the window button is placed on the taskbar, create the window by calling CreateWindowEx and include the WS_EX_APPWINDOW style. To prevent the window button from being placed on the taskbar, create the window by calling CreateWindowEx and include the WS_EX_TOOLWINDOW style. As an alternative, you can create a hidden window and make it the owner of your primary window.
The window button typically contains the application icon and title. However, if the application does not contain a window menu, the window button is created without the icon.
If you want your application to display a message to the user while its window is not active, use the FlashWindow function to let the user know that a message is waiting. This function flashes the window button. Once the user clicks the window button to activate the window, your application can display the message.