DotNetNuke is an open source platform for building web sites based on Microsoft .NET technology. DotNetNuke is written in VB.NET and distributed under both a Community Edition BSD-style license and a Professional Edition proprietary license. DotNetNuke's content management system is extensible and customizable through the use of skins, modules, data providers, language packs and templates.
Are you a web-developer and tired of using FIREBUG on firefox to check what error message or issues on your wesbite? Atleast it is for me as i dont like the idea of installing FireBug to identify problem when developing a site.The Markup Validator is a free service by W3C that helps check the validity of Web documents.