<style>
#main {
	width: 300px;
}

#nested {
	border: 1px solid red;
	display: block;
	height: 50%;
	width: 50px;
}

</style>

<div id=main>first line with<div id=nested style="float: left">float</div>content</div>
<div style="height: 100px">second line with<div id=nested style="display: inline-block">inline block</div>content</div>