Good catch.

Edit any of the H3 elements in any of the gray rows and simulate a tooltip:

<h3>col-1-1</h3>

Replace it in Firebug with a basic tooltip:

<h3 style="position:relative"> col-1-2 <span style="border:1px solid blue;background:yellow;display:block;position:absolute;width:300px;height:50px;left:0;top:-55px">Hi there</span> </h3>

The tooltips get cut off. :(