Form resize

Even if form Align property is set to alClient form is not resized in the browser so that it fits the entire space. It's width and height still remains as in the design time.

How to resize the form so that it's size really is the entire space available in the browser?

The main active form is by default always the full browser client size.
See Align demo. 
What are you doing different from this?

1. Place a button at the lower-right end of the form.
2. Click on the Form and set it's 'Allign' property to alBottom or alClient

When running the application the button is in the same position as in design-mode instead at the lower-right end of the web browser page. I don't want to use button align property as it will completely change width/height of the control.

I'm not sure how you expect this to work. In a VCL application the behavior is the same. The button remains in the design-time position.

Maybe you don't understand me correctly.

Notice that the button is at the lower-right end of the design surface and it has Right & Bottom anchors only. When I run the application I get:

Form has Align set to alClient.