How can I prevent overlap of two "spanX" divs when shrinking the screen in Bootstrap? <p>I am using the <code>responsive</code> layout of Twitter Bootstrap 2.3. I have a <code>span9 row-fluid</code> div containing two <code>span4</code> divs.</p> <p>To test the fluidity of the screen, I'm shrinking the window. There comes a specific point at which the right <code>span4</code> overlaps with the left <code>span4</code>. If I keep shrinking the window, it will stack appropriately. But I want it to stack appropriately before overlapping. Is the functionality I want built into Bootstrap and I'm just not doing it right?</p> <p>Any help is appreciated of course!</p>