When making a site live, its useful to be able to update it easily from Subversion systems, i.e. checking out straight into a web accessible area (your public_html for example).

However, doing so could potentially be dangerous dependent on you Apache (IIS, Lighty etc) setup. For example, you could go to a publically accessible folder and then find the subversion dot files .svn/entries as an example.

To protect against this, it is wise to block Apache from allowing users to see these files, they have no need to see them at all so blanket blocking them on your server is definitely worth while.

Adding the following little block to your apache.conf (or httpd.conf) will block users being able to see any .svn folder and files within it, protecting possible sensitive data escaping.