This is not standard practice. It might be needed or useful in some cases.
We place the drupal code into a subdirectory under the site's root. At the same time we want all access to the site to be as usual, direct, so that the code directory does not appear in the site's address bar.
This can be done. We need to a) redirect the site to the subdirectory that we created to contain the code and b) tell the code to bypass the subdirectory name.
Sources:
http://drupal.org/node/144643 the first post works, the comments mention other variants for slightly different purposes.
http://acquia.com/node/952011 based on the above source, but slightly different, apparently by acquia drupal professionals. here the www is dropped.
Note: Generally, it's best practice to place the code directly under root. The fixes needed to bypass a specific drupal code subdirectory might possibly have negative side effects for search engine visibility. Since this is not really certain, it's wise to stick with best practice.