Registering a Web Part Assembly as a Safe Control
To register a Web Part as a safe control for use in Microsoft® Windows® SharePoint™ Services, add a SafeControl element that specifies the Web Part in the top-level web.config file of the deployment or virtual server. For information on how to register a Web Part assembly, see Creating a Basic Web Part.
Warning Changes that you make to web.config may be overwritten when you install updates or service packs for Windows SharePoint Services, or when you upgrade an installation to the next product version.
For general information about the web.config files used in a Windows SharePoint Services deployment, see Working with web.config Files.