You should see two green rectangles next to each other with a blue outline. If you can see the red background the the browser has the bug. There should be no scroll bars if a scroll bar is visible this is incorrect. See outline in the css 2.1 spec.

The same floats but without the outline are below.

the same again but this time without floating the contained divs

css used shown below

div { background-color: green; color: white; width: 100px; float: left; } div.container { float: none; width: 200px; background-color: red; overflow: auto } div#container-1 div { outline: 3px solid blue; } div#container-2 div { outline: 3px solid blue; float: none; width: auto; margin: 0 } div#container-2 div p { margin: 0 }