myid1

myid2: this won't float up (in gecko mode). only the content will wrap which makes it look like it is floating up. but it really isn't.

myid1a

myid2a: the only difference between this and myid2 is that I've cleared the float this time. when i clear the float neither the content or the containing div wrap up

myid3

myid4: here is an element that is styled just like myid2 only this time I've floated it. reduce the size of the browser enough and you will see it fall below myid3. but it will float up and to the left if there is space. as per http://www.w3.org/TR/CSS2/visuren.html#propdef-float a left-floating box must be put as far to the left as possible, a right-floating box as far to the right as possible. A higher position is preferred over one that is further to the left/right.