Paragraph 1. This paragraph has the normal behavior of a block-level element. It takes up the entire width of the page, and the next element is placed underneath.
Paragraph 2. This paragraph is floated left. The next element will be placed to the right of it. Now this has a width of 50%.
Paragraph 3. This paragraph now has a margin-left so it is separated from the previous paragraph. It's width is still automatically determined.