You can use the Custom Extension Web item to display information related to the current navigational state of a data provider or the results set, or to integrate your own HTML or JavaScript into a Web template. You do this by creating an ABAP class that you then integrate in the Web template using a parameter from the Web item.
You have created an ABAP class that makes it possible to display HTML, JavaScript or PDF. More information: Creating an ABAP Class for the Custom Extension Web Item
You have inserted the Custom ExtensionWeb item into a Web template of your choosing. If you call the Web template in the Web browser, your own HTML or JavaScript is inserted.
More information:
The following examples of how to use the Custom Extension Web item are available:
Simple Example: Displaying a Simple Text and Parameter
Complex Example: Displaying the XML of Two Data Providers