You can customize the look and feel of the content block of the window by specifying the contentStyle property.
<window title="My Window" border="normal" width="200px" contentStyle="background:yellow">Hello, World! </window>
A typical use of contentStyle is to make a window scrollable as follows.
<window id="win" title="Hi" width="150px" height="100px" contentStyle="overflow:auto" border="normal"> This is a long line to spead over several lines, and more content to display. Finally, the scrollbar becomes visible.This is another line. </window>