[TYPO3-english] How to fix max image width for page content?

[Benoit Montereau]

My webpages are composed of different "contents/blocks". In order to keep
the display ok, I need to be sure that for all pages my editors will not be
able to set/define themselves the width of the inserted images.

For content type "Text and image" I would like my user can ONLY use
left/right with text and I also would like to fix the maximum width
(display) of the image they can insert.

The same way, for blocks "Images only", I would fix the maximum width of the
images they will insert.

Is it something possible? Do I need to define these constant with
Typoscript, where?
Thanks in advance for your help.
BM