Default: null.
Default: "normal".
Default: null. If null, the button has no function unless you specify the onClick event listener.
If it is not null, the onClick event won't be sent.
Default: "horizontal".
Default: -1 (means the same as browser's default).
Note: it is useful only if href ( Button.setHref ) is specified (i.e., use the onClick listener).
Default: false.
This method has no real effect. See w3.org