Does anyone know what an Error Type: Value Error, Error Value:Invalid Header (0) error represents ? It's interesting in the way it shows itself up. I added a <dtml-var a_dtml_method> to a dtml method and it generates this error. This <dtml-var a_dtml_method> is nested inside a <dtml-if> and would definitely not be rendered the first time the 'calling' dtml-method is rendered. I took out the <dtml-var a_dtml_method> and I still got the same error. I put a <dtml-var REQUEST> as the first line of the 'calling' method and everything then renders correctly with no error. Even the <dtml-var a_dtml_method> renders correctly when it should do so. Any ideas, suggestions ? I'm running Zope 2.1.6 on RedHat Linux Thanks Richard Richard Moon richard@dcs.co.uk