Update INSTALL.md

doc/INSTALL.md

@@ -1,26 +1,37 @@
 ## INSTALL
 
-### Manual installation
+#### Chromium
 
-- Download and unzip `uMatrix.chromium-{version}.zip` ([latest release desirable](https://github.com/gorhill/uMatrix/releases)).
-- Rename the unzipped directory to `uMatrix` (if it is different)
-    - When you later update manually, replace the **content** of the `uMatrix` folder with the **content** of the latest zipped version.
+- Download and unzip `uMatrix.chromium.zip` ([latest release desirable](https://github.com/gorhill/uMatrix/releases)).
+- Rename the unzipped directory to `umatrix`
+    - When you later update manually, replace the **content** of the `umatrix` folder with the **content** of the latest zipped version.
     - This will ensure that all the extension settings will be preserved
     - As long as the extension loads **from same folder path from which it was originally installed**, all your settings will be preserved.
 - Go to chromium/chrome *Extensions*.
 - Click to check *Developer mode*.
 - Click *Load unpacked extension...*.
 - In the file selector dialog:
-    - Select the directory `uMatrix` which was created above.
+    - Select the directory `umatrix` which was created above.
     - Click *Open*.
 
 The extension will now be available in your chromium/chromium-based browser.
 
 Remember that you have to update manually also. For some users, updating manually is actually an advantage because:
 - You can update when **you** want
-- If ever a new version sucks, you can easily just re-installed the previous one
+- If ever a new version sucks, you can easily just re-install the previous one
 
-### Vendor stores
+#### Firefox
 
-- Opera store (coming)
-- Chrome store (coming)
+Although uMatrix is a restartless addon, I found that **installing** a newer version over an older one often will glitch the installation. These steps always worked fine:
+
+- Download `uMatrix.firefox.xpi` ([latest release desirable](https://github.com/gorhill/uMatrix/releases)). 
+- Uninstall current uMatrix if already installed
+- Quit Firefox completely
+- Launch Firefox
+- Drag and drop the previously downloaded `uMatrix.firefox.xpi` into Firefox
+
+uMatrix settings are kept intact even after you uninstall the addon.
+
+On Linux, the settings are saved in a SQlite file located at `~/.mozilla/firefox/[profile name]/extension-data/umatrix.sqlite`.
+
+On Windows, the settings are saved in a SQlite file located at `%APPDATA%\Mozilla\Firefox\Profiles\[profile name]\extension-data\umatrix.sqlite`.