Where is my Z?

This box is identical to the next one in all respects except one. This holder has no explicit z-index given. This for some reason makes the .PNG backgrounds (which are identical images) have different alpha-opacity. This is even more complex, because it only occurs IF position:relative is used to define placement of the box (i.e. setting float:left or any other position value kills the bug). Tested in Opera V7b2 (build:2577)

Ha, I know my Z!

This box is identical to the first apart from a z-index:5 having been declared for it. Notice how, even though the PNG background image defined in the CSS is identical, the transparency appears different from the first box.

I feel static, but its better than being a relativist...

This box is identical to the first box apart from position:static having been declared for it. Again, even though the PNG background image defined in the CSS is identical, the transparency appears different from the first box.