During the web development process errors and cross browser inconsistencies are inevitable.

Sometimes these are simply a matter of the someone viewing a page while you are in the process of uploading the supporting files. Just refreshing a page while you are overwriting the style sheet can leave a user with a page that displays with no CSS at all. For a professional web developer and for most clients this is unacceptable on a live website.

For most of the live websites that I work on, whether it be maintenance, adding functionality, or even a complete redesign, I like to create a duplicate of the entire website including all files and the database on the same server.

While I generally develop using a local setup of PHP and MySQL on my workstation, I will sometimes run into conflicts when I post the website to the client server. These errors can be from different server configuration settings (including magic quotes, session lifetimes, upload file sizes, and argument separators), programming language or database version conflicts, or OS differences. For this reason I prefer to deploy to a duplicate of the website on the target server itself for the second round of testing.