<h:form id="form">
            <p:dataGrid var="category" value="#{navigationController.categories}" columns="4" layout="grid"
                        rows="16" id="cars">
                <f:facet name="header">
                    Cars for Sale
                </f:facet>
                <p:commandLink action="pretty:viewCategory">
                    <p:panel header="#{category.id}" style="text-align:center">
                        <h:panelGrid columns="1" style="width:100%">
                            <p:graphicImage library="indexImages" name="#{category.imageName}"/> 
                            <h:outputText value="#{category.categoryName}" />
                        </h:panelGrid>
                    </p:panel>
                    <f:param name="pageName" value="#{category.categoryName}" />
                </p:commandLink>
            </p:dataGrid>
        </h:form>