public class EmpDetails extends LayoutContainer {


private VerticalPanel EmpVP;
private FormData formData;

public EmpDetails() {

    formData = new FormData("-20");

    EmpVP = new VerticalPanel();
    EmpVP.setSpacing(10);
    createForm();
    setLayout(new CenterLayout());
    add(EmpVP);
}


private void createForm() {// some textboxes and radio button from demo example}

public EmpDetails() {

    formData = new FormData("-20");

    empVP = new VerticalPanel();
    empVP.setStyleName("topPanel");
    empVP.setSpacing(10);
    createForm();
    empVP.setHorizontalAlign(HorizontalAlignment.CENTER);

    add(empVP);
}

.topPanel > table{
    width:100%;
}

FormPanel simple = new FormPanel();
    ...
    simple.setStyleAttribute("text-align", "left");

DOM.setStyleAttribute(empVP.getElement(), "marginLeft", "auto");
DOM.setStyleAttribute(empVP.getElement(), "marginRight", "auto");

DOM.setStyleAttribute(this.getElement(), "marginLeft", "auto");
DOM.setStyleAttribute(this.getElement(), "marginRight", "auto");