Why does CSS float not change the width of the following div?

Question

As I understand float:left, it will push the subsequent element to its left rather than on a new line.

In the following example I would expect that the

Answer 1

CSS:

.inline {
    float:left;
    position:relative;
    width:auto
}

.yellow {
    background-color:yellow;
    position:relative;
    float:left;
}

see fiddle