When uploading images via the media manager there are a couple of set sizes available such as thumb, medium and large.
I do know how to add additional sizes, but I have yet to get it to insert an image with width='x%'.
the concept is that i am building an adaptive theme and I never want the inserted image to be larger than the container even upon browser resize,
By manually editing the inserted image code to include widths with a %, then it works just fine. However trying to get my users to remember this is downright impossible.
What I would like would be a button to insert an image into a post with a set % (percentage) instead of a set pixel width.