Locking APT packages to spesific version
I never knew this until i was really need this. My Firefox automatically upgraded and some of the add-on became incompatible.
If you are using synaptic, you can force a package to specific version. Select
Packages -> Force Version
Then, you ll be given option to use which version to use.
To lock the package from being upgraded. You can lock the package by select the specific package, then select
Packages -> Lock Version
Quite simple and useful. However only do this when u are really needed to.