Out of interest, can you tell me which theme are you using, is it one of the APEX built-in ones, or something custom? I searched our 4.2.3 code base for such references and found none, so perhaps this is either from a legacy theme, or do you know if it has been customised?
Thanks for getting back to me. We're using Apex 4.2.1, theme 22 (bluejay) and had customised the button template by adding the href="#LINK#" attribute.
No worries, and thanks for the information.