I don't know why everyone recommends moving, renaming or deleting ~/.mozilla folder to solve Firefox issues. The ~/.mozilla folder is also the place where other Mozilla applications stores their profiles (Thunderbird, Sunbird, etc), so deleting this folder will delete their settings too.
Firefox profiles are stored under ~/.mozilla/firefox folder. So if you need to remove a Firefox profile to fix a problem, then delete, rename or move ~/.mozilla/firefox not ~/.mozilla. Nevertheless, removing an entire profile is usually unnecessary and must be avoided, since just a few profile files are the usual culprits, otherwise you will remove all Firefox settings, extensions, themes, bookmarks and so on.