Developing Drupal in a development--test--production environment has a lot of advantages. Each developer's work is sandboxed, staging is straightforward, and deployment to live the stuff of Capistrano scripts---especially if you unite the entire ecosystem of separate environments with version control.
However, it can lead to confusion over precisely where your browser's currently pointing at: at best, this can be comical; at worst, it can result in either loss of live content or the logjamming of a staged site with content intended for live. Suddenly a staging environment is out of action until that content can be exported to the live site.
Enter devwatermark β-0.1, a D5 module intended to watermark any non-live sites with a little right-hand banner overlay. When first enabled---you can do this on your live site---it inserts no such banner. However, as you add live domains to its configuration, it begins to work out when it's not on a live site and tags your browser window with the "DEVELOPMENT" banner. Like watermarking your printouts with "DRAFT", or maybe like dogearing a page in a book. If your site has to respond to multiple domains---and if the content is the same then you should really serve up 301s instead---then you can add those extra domains to the configuration as required.
Having devwatermark enabled on live means that when you bring a live database down to a staging site to test the next round of updates, the change in domain will make devwatermark automatically show its banner image. You know instantly when you're in a development---and hence content-volatile---environment. That means that you can also watermark staging sites as non-development too: by adding them to devwatermark's configuration you can confirm to the developers that here's a database environment that they can't wipe and start again.
As I mention above, it's currently only available for Drupal 5, and your theme has to respect hook_footer (most do out of the box.) But please feel free to download it and give it a try.
