What happened with Jquery removeOption

I have an error in my code - Object doesn't support this property or method when calling removeOption on a JQuery selector. I cannot find this function in the Jquery API. Is that some old method that is now obsolete? What is the new version? Jquery version is 1.3.2

The technique is shown here: http://www.texotela.co.uk/code/jquery/sel开发者_开发问答ect/

It really was the selectboxes plugin missing, thanks lonesomeday for that. @lonesomeday if you add an answer I will acceprt it.