Dear, sorry for my bad English.
Thank you for your help.
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<a4j:commandButton id="idLinkModificarUser"
action="#{administrationUserBean.alterUser}"
onclick="javascript:Richfaces.showModalPanel('idPanelAlterUser',{width:620,height:200})"
reRender="alterUserForm" image="/_commons/images/buttons/modificar_off.gif">
<f:param value="#{administrationUser.id}" name="inputUserId"/>
</a4j:commandButton>
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Regards
Cehu
Any errors in the developer console?