Make Child Div Float Right of Parent

I'd like to make an inner div float right of the parent, regardless of the width of the parent. An example of what this looks like is here: http://jsfiddle.net/eqDyy/. That fiddle is just an example of what it should look like. It's done with the exact number of pixels given, but what I'm looking for is a solution that still lets that inner div appear to the right of its parent, even when the parent width changes. The following is the code used in the fiddle: HTML ``` <div id="one"> <div id="two"></div> </div> ``` CSS ``` #one { border:2px solid #ddd; width:150px; height:30px; } #two { border:2px solid #ddd; width:150px; height:30px; margin-left:150px; margin-top:-2px; } ``` Again, please remember that this is just to show what I'd like it to look like, but it isn't a satisfying implementation because it uses specific pixel amounts.