The red vertical line is within the yellow container, floated right. The green boxes are outside of it, floated right. The yellow container is not floated. Every element is a div with hardcoded height and width. Try to understand why the red line is rendered outside of the yellow container. There are three ways to fix the problem:
- Assign "overflow:hidden" to the yellow box.
- Remove one of the green boxes.
- Assign "display:inline-block" to the yellow box.