I have Ubuntu 11.10 and for no apparent reason my sidebar suddenly will not hide, I did not go into system settings or anything like that. I googled this, but everything I found had me downloading something to be able to fix it. However, as it changed without me downloading anything, I'm hoping it's possible to change it back without downloading anything. I read somewhere that I should go into "System setting", "appearance", "behaviour" and change it to "auto-hide", but I did not have a "behaviour" tab in "appearance". I would normally be able to just deal with it, but it is preventing me from being able to click the "back" button when I am in a browser. Does anyone
The Behaviour tab is only in 12.04. The auto-hide was buggy that is why it was dropped in 12.04. The auto-hide sometimes got stuck If you have logged out and back in or rebooted your computer and it still doesn't work, you may have to download "My Unity" Instructions found here
I never had any problem in 11.10 getting the launcher to reset by logging out and back in or rebooting but, if for some reason your dconf setting got corrupted, you should be able to fix it using My Unity. Just select the behavior drop-down on the launcher tab.
There are other programs out there to adjust the dconf settings but My Unity is probably the safest and easiest to use.