Sometimes you may experience problems with configuration files, especially when you edit them manually ;)
It's generally a good habbit to keep track of all these changes, for example using git or svn. Git is more comfortable for me.
To create a git repository for /etc, you may use following commands (needs root privileges):
git add -A
git commit -a -m "Initial commit"
Than, at any time you may look at changes using
sudo git status
sudo git diff | gvim -
To add file to repository, use
sudo git add <filename>
And commit changes using
sudo git commit -a -m "some comment"
Note: You should definitely read some documentation on git before using it (there are many non-intuitive behaviors).
And remember: better to train your skills on some not important directories first ;)