css float/positioniong

Question

So I have a small div for the border, and three divs inside (see image at end). Green is full size (minus padding etc); Blue should float left and have specific width; Red should float right and also have a specific width. However I'm messing something up. Both of the blue and red divs float outside the main div. What am I doing wrong here?

Here's my current code:

<div style="border: 2px solid black; width: 630px;">
  <div style="width:auto;">Lorem ipsum</div>
  <div style="width:150px; float:left;">This is the blue box</div>
  <div style="width:150px; float:right;">This is the red box</div>
</div>

Answer 1

Positioning of floats is funny. Basically, the main div is not taking into account the height of the floated elements when figuring out its own height. The easiest way to resolve this is to add a clearing element after the floated elements.

This fiddle should explain itself clearly: http://jsfiddle.net/QQxb3/2/

I think that the folks who commented on your post saying that it does work must have misunderstood what you mean by "main div", because specification, which Chrome does follow and IE follows in this particular instance, would place the floated elements outside of its parent div.