[TYPO3] image width=100%

[Vandemaele David]

The template of my clients site contains a sidebar on each page. On  the 
old site, the width of the image is set to 100%.(I'm not sure if this is 
valid..., this aside).
My client wants to choose an image for each page on the fly.
Problem is Typo3 specifies a with and a height for the image. It even 
translates my 100% to auto.
Can I change this? Perhaps another solution? (Changing the attribute 
"src" of the image via Typoscript... dunno)

David