Richfaces layout

Question

I use Seam 2.1.2 and RichFaces 3.3.3

I have the following layout:

    <rich:layout id="myDiv" style="background-color:#ffffff; border:1px solid; margin:0:padding:0;height:100%">
      <rich:layoutPanel position="top">
        <div style="border:0px solid; margin:0px; padding:0px;
         height:105px; background-color:#ffffff;">
          <ui:insert name="top"/>           
        </div>
      </rich:layoutPanel>

      <rich:layoutPanel position="left" width="0px"/>
      <rich:layoutPanel position="right" width="0px"/>

      <rich:layoutPanel id='centerPanel' position="center" style="width:100%">
        <div style="border:0px solid;  height:100%; margin:5px; padding:1px">
            <ui:include src="/errorPage.xhtml"/>
            <ui:insert name="center"/>
        </div>
      </rich:layoutPanel>

      </rich:layout>

When I look with Firebug and only look at the centerPanel the generated html is:

<div style="float: left; width: 97.02%;" id="centerPanel">

</div>

Where does the 97.02% width come from? How can I make the centerPanel use 100% width?