All markup languages ( XML, (x)HTML, SGML, etc ) are hierarchies; text representing any type of information in a tree-like structure. WebDom Viewer shows the structure of a ML document of any type in a graphical, easy to understand way.
Pure XML is much more strict than most variants of HTML. While paragraph and image tags can be left open, and often are, extensible markup language doesn't allow this for any tag. So, while there are any number of XML tools on the web, many of them don't work against older ( and very common ) web pages.
WebDom Viewer understands broken markup, and can display the structure of a web page that doesn't conform to (X)HTML strict. It can also parse and drill down into compliant XML documents, so you can use WebDom Viewer to analyze messages to and from web services.
WebDom Viewer provides a unique, visual way to understand the structure of a document, or to debug problems in the markup.