Floating elements within a div, floats outside of div. Why?

Question

Say you have a div, give it a definite width and put elements in it, in my case an img and another div.

The idea

Answer 1

As Lucas says, what you are describing is the intended behaviour for the float property. What confuses many people is that float has been pushed well beyond its original intended usage in order to make up for shortcomings in the CSS layout model.

Have a look at Floatutorial if you'd like to get a better understanding of how this property works.