You can control where your XUL widgets will be inserted by using the position, insertbefore and insertafter attributes.
Here is an example:
<!-- This is the main box containing the statusbar --> <vbox id="browser-bottombox"> <label value="One" position="1" /> <label value="Two" insertbefore="status-bar" /> <label value="Three" insertafter="status-bar" /> </vbox> <!-- The output will look like the following: One Two the status bar here Three -->