Change the width of inserted post images

[vexxy]

I've noticed that if someone inserts an image within a post (outside image, not attachment), the images stretch as big as they are, extending over my layout. How can I set a fixed width to those images? I didn't found its CSS class... I also wish to add the link to their own external url location, for users to click and see the full width image.

--------------- Added [DATE]1271361368[/DATE] at [TIME]1271361368[/TIME] ---------------

so, no clues with this issue?