Widgets and panels work the same way on all browsers; by using them, you eliminate the need to write specialized code for each browser. But you are not limited to the set of widgets provided by the toolkit. There are a number of ways to create custom widgets yourself.
Panels, such as DockPanel, HorizontalPanel, and RootPanel, contain widgets and are used to define how they are laid out in the browser.
Visual styles are applied to widgets using Cascading Style Sheets (CSS). This section describes in detail how to use this feature.