gecko-dev/xpinstall/res/content/xpistatus.xul

<?xml version="1.0"?> 
<?xml-stylesheet href="resource:/res/xpinstall/xpistatus.css" type="text/css"?> 
<!DOCTYPE window SYSTEM "chrome://xpinstall/locale/xpistatus.dtd" >


<window xmlns:html="http://www.w3.org/TR/REC-html40"
        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
        onload="onLoad()"
        title="Items to Install"> 

    <html:script language="javascript" src="xpistatus.js">
    </html:script>
  
    <box align="vertical" style="height: 30%; width: 50%">

        <box align="horizontal">
          <box align="horizontal" flex="100%" >
            <html:div> <html:h3> &dialogTitle.label; </html:h3> </html:div>
          </box>
          <spring flex="100%"/>
          <box align="horizontal">
            <html:img src="resource:/res/throbber/anims00.gif"/>
          </box>
        </box>

        <box align="vertical">
          <html:div style="height:10px; width:100%"><html:hr/></html:div>
        </box>

        <box align="horizontal">
          <spring style="width:10px"/>  
          <html:div> <html:h5> &currentlyProcessing.text; </html:h5> </html:div>
        </box>

        <spring style="height:10px"/>  

        <box align="horizontal">  
          <spring style="width:10px"/>  
          <html:div> &downloadBeforeUpdate.text; </html:div>
        </box>

        <spring style="height:20px"></spring>

        <box align="horizontal">
          <spring style="width:10px"/>
          <box align="vertical">
            <spring style="height:6px"/>
            <progressmeter id="dialog.progress" mode="undetermined" style="width:200px;height:10px">
            </progressmeter>
          </box>
          <box align="horizontal">
            <html:button id="dialog.cancel" onclick="cancel()">&dialogCancel.label;</html:button>
          </box>
        </box>

    </box>

</window>