The search design works fine until we get down to our “baby bear” (small mobile) size break. We have to do something different there. We make some room for it below the navigation area and then move it down into that space with absolute positioning.
We have a bunch of tweaks to do to make this somewhat drastic shift in location. We change sizing and spacing and colors and everything. What is cool is that at least we don’t have to repeat markup to do this, we’re reusing the exact search form markup everywhere. That’s the power of CSS coming through for us.
Did you ever figure out why you needed z-index on the search area? I realize that the main content area comes after the search (and so would be stacked on top) but as you alluded, it’s absolutely positioned, so it shouldn’t need it.