See also Firefox-dark-themes
When opening a new tab in Firefox, the default is to show a search page. I think that's stupid, and so I make it completely blank. Edit > Preferences > General and for Home Page I type about:blank.
So instead of using the new tab search page, I type my search terms in the location bar. But by default it does an "I'm feeling lucky" search. To change that behaviour, I go to about:config and change keyword.URL to http://www.google.com/search?ie=UTF-8&oe=UTF-8&sourceid=navclient&gfns=0&q=
So now the top-right search area is redundant. To remove it, right_click beside the top location bar and select "customize". Drag the top "search" area into the middle area and drop it.
But now I'm left with an about:blank that's bright white. Since my dark theme (still [1] NASA Night Launch) does not change that colour (perhaps it cannot?) I need to do it myself. Thankfully others have already thought of this:
Done! Just one more thing to save my eyes a little bit. I haven't done much more research on dark theming, but it's never going to drop off my radar.. so more will trickle through.I don't know why they bothered with a screenshot.