UI components accessing problem when using Word Space as Canvas Render mode

I am new to Unity3d and creating scroll view with the help of NGUI scroll view example scene. I placed the UI Button and add Canvas component and selected "Word Space" as Canvas Render mode because all other components are in this mode. But I could not access the button using mouse click. Then I changed the Canvas Render mode to "Screen Space - Overlay" mode, I can access the UI button. But when I changing the screen size, the location of the button changed and gone outside of the frame. It...

UI components accessing problem when using Word Space as Canvas Render mode