Figuring out DOM for JavaScript is a little bit tricky because of browser incompatibilities. Although you should be able to load an Ajax based application in most browsers, the reaction of different browsers to JavaScript is different. Developers have to create modifications in their application most of the time if they wanted to ensure that their application is readable in all browsers. Without modifications, the application will not be able to adapt to different browsers and may even open up to different security questions. One of the reasons of browser incompatibility is in the variations of document types in DOM. There are developers who prefer to launch a specific