In some cases you need the options of your selectbox to be made of a code and a label, but separated by spaces so all labels are aligned. To do this you can use a monospace font, and add the right amount of spaces (rightpad). Be sure to tell JSF to not escape the labels. I also had to implement my own converter.

MyJsfHelper.java

/**
 * return a list of JSF SelectItem made of a code and a
 * label, separated by spaces. All the labels are aligned 
 * (depending you use a monospace font)
 */
@Factory(value = "codeSelectItemList", scope = ScopeType.SESSION)
public List<SelectItem> getFixedSizeSelectItems(){
  int padSize = 8;
  String padChar = StringEscapeUtils.unescapeHtml("&nbsp;");
  
  List<RefCode> refList = (List<RefCode>) refCodeDao.loadAll();
  List<SelectItem> refSelectItemList = new ArrayList<SelectItem>();
  
  for (RefCode r : refList) {
  	SelectItem si = new SelectItem(r, StringUtils.rightPad(r.getCode(), padSize, padChar).concat(r.getLabel()));
  	refSelectItemList.add(si);
  }
  
  return refSelectItemList;
}

MySelectItemConverter.java

import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.convert.Converter;
import javax.faces.convert.ConverterException;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.validator.GenericValidator;
import org.jboss.seam.Component;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.intercept.BypassInterceptors;

@Name("mySelectItemConverter")
@BypassInterceptors
public class MySelectItemConverter implements Converter {

  @Override
	public Object getAsObject(FacesContext context, UIComponent component,
			String value) {
		RefCodeDao refCodeDao = (RefCodeDao) Component
				.getInstance("reference.codeDao");

		RefCode refCode = null;
		if (StringUtils.isNotBlank(value) && GenericValidator.isLong(value)) {
			try {
				refCode = refCodeDao.load(Long.valueOf(value));
			} catch (Exception e) {
				// catch any exception
				throw new ConverterException("Erreur de conversion");
			}
		}

		return refCode;
	}

	@Override
	public String getAsString(FacesContext context, UIComponent component,
			Object value) {
		String valueOut = null;
		if (value != null) {
			valueOut = ((RefCode) value).getId().toString();
		}

		return valueOut;
	}
}

page.xhtml

<h:selectOneMenu value="#{code}"
	converter="mySelectItemConverter"
	styleClass="monospace">
	<f:selectItem itemLabel="-" />
	<f:selectItems
		value="#{codeSelectItemList}"
		itemLabelEscaped="false" noSelectionValue="" />
</h:selectOneMenu>