I was messing around with the HTML templates and CSS style sheets for the homepage of our working group in order to get rid off some graphical issues and get ready for HTML5 and CSS3. During this process I made a big discovery:

In the template there is a <div> container that shall have the same width (CSS style: width: 100%; or width: 840px;) as its parent <div> container. But this container does not behave in the intended manner, unless...

Without border definition
Figure: <div> container containing a series of <img>s and width of 100%. In the CSS style sheet is no border defined.

With border definition
Figure: Identical <div> container as in the previous figure, but with a border (solid 1px #000) defined in the CSS style sheet. Like a miracle the container is behaving as expected.

I would like to conclude that the border attribute of CSS style sheets is more important than just drawing a stupid line around the HTML object. Is this a bug in my browser or is it a feature?