For styling purposes I would like to add the nodename as the id for each li in my navigation.  I have it working except I need to strip the spaces so that I can use css for styling.  How can I strip the spaces?

<code>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xsl:stylesheet [
    <!ENTITY nbsp "&#x00A0;">
]>
<xsl:stylesheet
    version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:msxml="urn:schemas-microsoft-com:xslt"
    xmlns:umbraco.library="urn:umbraco.library"
    exclude-result-prefixes="msxml umbraco.library">


    <xsl:output method="xml" omit-xml-declaration="yes"/>

    <xsl:param name="currentPage"/>

    <xsl:template match="/">

        <ul id="navi">

            <xsl:variable name="rootNode" select="$currentPage/ancestor-or-self::node [@level=1]" />
           
            <li>
              <!--
                  Add the ID to equal the nodeName for styling purposes
              -->
              <xsl:attribute name="ID">
                <xsl:value-of select="$rootNode/@nodeName" />
              </xsl:attribute>
                <!--
                    Add the class selected if the root node ID matches our
                    current node ID in the for each loop
                 -->
                <xsl:if test="$rootNode/@id = $currentPage/@id">
                    <xsl:attribute name="class">
                        <xsl:text>
                            selected
                        </xsl:text>
                    </xsl:attribute>
  
                </xsl:if>
               
                <a href="{umbraco.library:NiceUrl($rootNode/@id)}">
                    <xsl:value-of select="$rootNode/@nodeName" />
                </a>
            </li>
           
            <xsl:for-each select="$currentPage/ancestor-or-self::node/node [@level = 2 and string(data[@alias='umbracoNaviHide']) != '1']">
                <li>
                <!--
                  Add the ID to equal the nodeName for styling purposes
                -->
                  <xsl:attribute name="ID">
                    <xsl:value-of select="@nodeName" />
                  </xsl:attribute>
                  <!--
                    Add the class selected if the currentpage or parent nodes (up the tree to the root)
                    ID matches our current node ID in the for each loop
                  -->
                    <xsl:if test="$currentPage/ancestor-or-self::node/@id = current()/@id">
                        <xsl:attribute name="class">
                            <xsl:text>
                                selected
                            </xsl:text>
                        </xsl:attribute>
                    </xsl:if>
                   
                    <a href="{umbraco.library:NiceUrl(@id)}">
                        <xsl:value-of select="@nodeName" />
                    </a>
                </li>
            </xsl:for-each>
        </ul>

    </xsl:template>

</xsl:stylesheet>

</code>