Div height question

Div height question

Hello all

The link to jsfiddle shows something I don't understand.

The div with the blue backgrounder not automatically grow in size to contain the input field.  I have set the height to 20px so itat least shows up.

Without the size explicitly set it won't show up at all.

Can anyone explain why?  Is this a case thing or does it have to do with jQuery/jQuery Mobile?


Link to jsfiddle