Back | View Source (use the "Back-button" in your browser to go back)

Float left

This is the first block-level element, flow is from top to bottom and elements are expanded over the complete width of the webpage
This is the second element which is floated to the left and still placed in the normal flow.
Finally, we have the third element which now has a "clear: left" style and does not use the space at the right-side of the second element. It continues normal flow underneath the second element.
To make things a bit more comprehensive we here have a fourth block-level element which also floats to the left. But this does not effect the flow of the third element.