Primary tags
At a minimum, all your web pages will need to contain the <html>, <head>, and <body> tags. The <html> tag defines the whole HTML document. All other tags must be placed inside this tag. Tags that define how the web page will appear in the browser are placed inside the <body> tag. For instance, your mapping applications will contain a <div> tag inside the <body> tag that is used as a container for displaying the map.
Loading this HTML page in a browser would produce the content you see in the following screenshot. Most of the ArcGIS API for JavaScript code that you write will be placed between the <head></head> tags, either within a <script> tag or inside a separate JavaScript file. As you gain experience you will likely begin placing your JavaScript code inside one or more JavaScript files and then referencing them from the <head> section. We'll explore this topic later. For now just concentrate on placing your code inside <script> tags, within the <head> tags:
