You don’t want to display all your errors for the world to see so when you create web page you will want to check that they actually display correctly before you upload them to the web.
Testing Server Side Processing Before you Upload

The initial series of tutorials on using NVU to create standards compliant web pages comes to an end with this eleventh tutorial which covers how to actually publish the pages that you have created to your web site. At this point if you have worked your way through from tutorial one you will know how [...]