Fixing Firefox default monitor

October 26, 2009

I’m running Firefox 3.0.14 on Mac OS X 10.5.

I’ve got a MacBook laptop and a 24″ LCD display as my normal configuration, though sometimes I’m just using the laptop.

Whenever I open a new browser window, it defaults to the laptop display, not the big LCD, even though that’s my main screen.

I searched the forums, and didn’t find any good solution, so here’s what worked for me:

  1. Quit Firefox
  2. Locate the localstore.rdf file in your Firefox profile directory. This will be in the ~/Library/Application Support/Firefox/Profiles/<random string>.default/ directory.
  3. Open it with your favorite text editor.
  4. Find the RDF section with the description set to “chrome://browser/content/browser.xul#main-window”
  5. Set the screenX and screenY values to 0.
  6. Save the file.
  7. Restart Firefox

In my case, for example, the prior contents of this file were:

<RDF:Description RDF:about="chrome://browser/content/browser.xul#main-window"
    height="778"
    screenX="-1273"
    screenY="401"
    width="1276"
    sizemode="maximized" />

By setting screenX=”0″ and screenY=”0″, I was able to fix my problem.