Here's how to close the Error Console... Rated 5 out of 5 stars
For those reporting that they can't close the Error Console, it took me a bit to figure out, but do this. Open FEBE Options. Click on the Advanced Tab. Click the Miscellaneous sub-tab. Uncheck "FEBE Debug Mode". Excellent Add-on!
REPLY TO AUTHOR - Thanks Chuck. Actually I was so shocked when this happened. I thought it was caused by another extension that I had installed called Console² 0.9. The screen looked very similar except it usually opens in its own box. I quickly closed the FEBE Welcome tab because I thought something was going on with that extension and I immediately disabled it. When that didn't fix it, I uninstalled it, but alas, it was still there even after restarting Firefox. Then that's when it hit me - it must be FEBE because it was the most recently updated add-on and just presented the Welcome page. So I poked around in the options and found the Debug box checked. And I didn't realize this was a major update until now. It just automatically updated and few of us endusers follow version numbers that closely. The ironic thing is, I'm usually one of those people that always read the changes in a new version whenever an updated add-on presents a welcome or thanks for updating page. But this time I was so distracted and frustrated by the Error Console and thinking it was another extension, that I immediately closed the tab to see if it would also close the console.
FEBE preferences should be cleared after any major update
Thanks for pointing this out. Another way to resolve this is to clear FEBE preferences.
In fact, on the FEBE Welcome page that is displayed after updating it states "Important: If you are upgrading from a previous FEBE major version or upgrading from a older Firefox version, you should clear your previous settings. Go to Tools > FEBE > FEBE Options > Advanced > Clear FEBE preferences."
This only needs to be done once after any major FEBE upgrade (which this is).