[Plone-UI] missing png tranparency - ie win workaround

[Peter Holzer]

hi
i'm trying to implement a workaround for the missing png transparency 
in internet explorer for windows
http://www.alistapart.com/articles/pngopacity/

the problem is that it only works in the template, if i access the code 
example as a html page.
http://one.agitator.com:10600/setareh/plone/opacity1/examples/ex1.htm

if i access a normal page, the workaround doesn't function.
http://one.agitator.com:10600/setareh/plone/

any idea what causes this strange behavior?
thanx
peter