I know this question is several years old, but what I think you're trying to do is get it so where a large element, like an image doesn't interfere with the height of a div?
I just ran into something similar, where I wanted an image to overflow a div, but I wanted it to be at the end of a string of text, so I didn't know where it would end up being.
A solution I figured out was to put the margin-bottom: -element's height, so if the image is 20px hight,
margin-bottom: -20px;
vertical-align: top;
for example.
That way it floated over the outside of the div, and stayed next to the last word in the string.