images don't resize

I’m running the latest version of WP, with the twentyten 1.1 theme.

Everything works fine, except that images (uploads or links) always display full size, whether I alter then via the image window or hard code the height & width via html. Experimenting in dreamweaver, the tag that seems to override the display size is <div id=”content” role=”main”>

If I save the web page to disk, then view it, the size behaves as I’d expect, so it must be some css setting?

Currently I have tressize the image manually, which is a pain.

Clues welcomed!