Why doesn't the percentage width child in absolutely positioned parent work?

Question :

I have an absolutely positioned div containing several children, one of which is a relatively positioned div. When I use a percentage-based width on the child div, it collapses to 0 width on IE7, but not on Firefox or Safari.
If I use pixel width, it works. If the parent is relatively positioned, the percentage width on the child works.

1. Is there something I'm missing here?
2. Is there an easy fix for this besides the pixel-based width on the child?
3. Is there an area of the CSS specification that covers this
   
   Answer :
   
   Does the parent div have a defined width either pixel or percentage? Not 100% sure but I think in IE7, the parent div needs a defined width for child percentage divs to work correctly.