XML documents do not carry information about how to display the data.
Since XML tags are "invented" by the author of the XML document, browsers do not know if a tag like <table> describes an HTML table or a dining table.
Without any information about how to display the data, most browsers will just display the XML document as it is.
In the next chapters, we will take a look at different solutions to the display problem, using CSS, XSL, JavaScript, and XML Data Islands.